Steps to reproduce the issue

I don't know if this is a bug or fault in my extension's updates server.
Install https://github.com/ramblerswebs/updates/blob/master/updates/downloads/ramblers-library-v1.2.0.zip
then see if site will update to next version 1.3.0
Joomla Update seems to find the latest version but does not list it as available

Expected result

Update should list version 1.3.0 as available

Actual result

nothing listed

System information (as much as possible)

PHP Built On Linux web236.extendcp.co.uk 2.6.32-573.8.1.el6.x86_64 #1 SMP Fri Sep 25 19:24:22 EDT 2015 x86_64
Database Version 5.5.35
Database Collation latin1_swedish_ci
PHP Version 5.5.30
Web Server Apache/2.4.18 (Unix)
WebServer to PHP Interface cgi-fcgi
Joomla! Version Joomla! 3.4.8 Stable [ Ember ] 24-December-2015 19:30 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
User Agent Mozilla/5.0 (Windows NT 10.0; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0

Additional comments

below is copy of the table _update which shows the new version of this extension as available. Plus loads of others.
I have other extensions that update ok, they are a plugin and modules. The only ones that don't seem to work are of type File.
I am probably doing something wrong but Joomla Update does find the update, not sure it does not list it as available when you do Find Updates

copy of _update table

INSERT INTO `i1oj4_updates` (`update_id`, `update_site_id`, `extension_id`, `name`, `description`, `element`, `type`, `folder`, `client_id`, `version`, `data`, `detailsurl`, `infourl`, `extra_query`) VALUES
(1, 3, 0, 'Armenian', '', 'pkg_hy-AM', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/hy-AM_details.xml', '', ''),
(2, 3, 0, 'Malay', '', 'pkg_ms-MY', 'package', '', 0, '3.4.1.2', '', 'http://update.joomla.org/language/details3/ms-MY_details.xml', '', ''),
(3, 3, 0, 'Romanian', '', 'pkg_ro-RO', 'package', '', 0, '3.4.3.1', '', 'http://update.joomla.org/language/details3/ro-RO_details.xml', '', ''),
(4, 3, 0, 'Flemish', '', 'pkg_nl-BE', 'package', '', 0, '3.4.8.2', '', 'http://update.joomla.org/language/details3/nl-BE_details.xml', '', ''),
(5, 3, 0, 'Chinese Traditional', '', 'pkg_zh-TW', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/zh-TW_details.xml', '', ''),
(6, 3, 0, 'French', '', 'pkg_fr-FR', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/fr-FR_details.xml', '', ''),
(7, 3, 0, 'Galician', '', 'pkg_gl-ES', 'package', '', 0, '3.3.1.2', '', 'http://update.joomla.org/language/details3/gl-ES_details.xml', '', ''),
(8, 3, 0, 'German', '', 'pkg_de-DE', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/de-DE_details.xml', '', ''),
(9, 3, 0, 'Greek', '', 'pkg_el-GR', 'package', '', 0, '3.4.2.1', '', 'http://update.joomla.org/language/details3/el-GR_details.xml', '', ''),
(10, 3, 0, 'Japanese', '', 'pkg_ja-JP', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/ja-JP_details.xml', '', ''),
(11, 3, 0, 'Hebrew', '', 'pkg_he-IL', 'package', '', 0, '3.1.1.1', '', 'http://update.joomla.org/language/details3/he-IL_details.xml', '', ''),
(12, 3, 0, 'Hungarian', '', 'pkg_hu-HU', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/hu-HU_details.xml', '', ''),
(13, 3, 0, 'Afrikaans', '', 'pkg_af-ZA', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/af-ZA_details.xml', '', ''),
(14, 3, 0, 'Arabic Unitag', '', 'pkg_ar-AA', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/ar-AA_details.xml', '', ''),
(15, 3, 0, 'Belarusian', '', 'pkg_be-BY', 'package', '', 0, '3.2.1.1', '', 'http://update.joomla.org/language/details3/be-BY_details.xml', '', ''),
(16, 3, 0, 'EnglishAU', '', 'pkg_en-AU', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/en-AU_details.xml', '', ''),
(17, 3, 0, 'Bulgarian', '', 'pkg_bg-BG', 'package', '', 0, '3.4.4.2', '', 'http://update.joomla.org/language/details3/bg-BG_details.xml', '', ''),
(18, 3, 0, 'Catalan', '', 'pkg_ca-ES', 'package', '', 0, '3.4.4.2', '', 'http://update.joomla.org/language/details3/ca-ES_details.xml', '', ''),
(19, 3, 0, 'Chinese Simplified', '', 'pkg_zh-CN', 'package', '', 0, '3.4.1.1', '', 'http://update.joomla.org/language/details3/zh-CN_details.xml', '', ''),
(20, 3, 0, 'EnglishUS', '', 'pkg_en-US', 'package', '', 0, '3.4.6.1', '', 'http://update.joomla.org/language/details3/en-US_details.xml', '', ''),
(21, 3, 0, 'Croatian', '', 'pkg_hr-HR', 'package', '', 0, '3.4.4.2', '', 'http://update.joomla.org/language/details3/hr-HR_details.xml', '', ''),
(22, 3, 0, 'Czech', '', 'pkg_cs-CZ', 'package', '', 0, '3.4.1.1', '', 'http://update.joomla.org/language/details3/cs-CZ_details.xml', '', ''),
(23, 3, 0, 'Danish', '', 'pkg_da-DK', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/da-DK_details.xml', '', ''),
(24, 3, 0, 'Dutch', '', 'pkg_nl-NL', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/nl-NL_details.xml', '', ''),
(25, 3, 0, 'Estonian', '', 'pkg_et-EE', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/et-EE_details.xml', '', ''),
(26, 3, 0, 'Italian', '', 'pkg_it-IT', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/it-IT_details.xml', '', ''),
(27, 3, 0, 'Khmer', '', 'pkg_km-KH', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/km-KH_details.xml', '', ''),
(28, 3, 0, 'Korean', '', 'pkg_ko-KR', 'package', '', 0, '3.4.4.2', '', 'http://update.joomla.org/language/details3/ko-KR_details.xml', '', ''),
(29, 3, 0, 'Latvian', '', 'pkg_lv-LV', 'package', '', 0, '3.4.3.1', '', 'http://update.joomla.org/language/details3/lv-LV_details.xml', '', ''),
(30, 3, 0, 'Macedonian', '', 'pkg_mk-MK', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/mk-MK_details.xml', '', ''),
(31, 3, 0, 'Norwegian Bokmal', '', 'pkg_nb-NO', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/nb-NO_details.xml', '', ''),
(32, 3, 0, 'Norwegian Nynorsk', '', 'pkg_nn-NO', 'package', '', 0, '3.4.2.1', '', 'http://update.joomla.org/language/details3/nn-NO_details.xml', '', ''),
(33, 3, 0, 'Persian', '', 'pkg_fa-IR', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/fa-IR_details.xml', '', ''),
(34, 3, 0, 'Polish', '', 'pkg_pl-PL', 'package', '', 0, '3.4.2.1', '', 'http://update.joomla.org/language/details3/pl-PL_details.xml', '', ''),
(35, 3, 0, 'Portuguese', '', 'pkg_pt-PT', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/pt-PT_details.xml', '', ''),
(36, 3, 0, 'Russian', '', 'pkg_ru-RU', 'package', '', 0, '3.4.1.3', '', 'http://update.joomla.org/language/details3/ru-RU_details.xml', '', ''),
(37, 3, 0, 'Slovak', '', 'pkg_sk-SK', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/sk-SK_details.xml', '', ''),
(38, 3, 0, 'Swedish', '', 'pkg_sv-SE', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/sv-SE_details.xml', '', ''),
(39, 3, 0, 'Syriac', '', 'pkg_sy-IQ', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/sy-IQ_details.xml', '', ''),
(40, 3, 0, 'Tamil', '', 'pkg_ta-IN', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/ta-IN_details.xml', '', ''),
(41, 3, 0, 'Thai', '', 'pkg_th-TH', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/th-TH_details.xml', '', ''),
(42, 3, 0, 'Turkish', '', 'pkg_tr-TR', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/tr-TR_details.xml', '', ''),
(43, 3, 0, 'Ukrainian', '', 'pkg_uk-UA', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/uk-UA_details.xml', '', ''),
(44, 3, 0, 'Uyghur', '', 'pkg_ug-CN', 'package', '', 0, '3.3.0.1', '', 'http://update.joomla.org/language/details3/ug-CN_details.xml', '', ''),
(45, 3, 0, 'Albanian', '', 'pkg_sq-AL', 'package', '', 0, '3.1.1.1', '', 'http://update.joomla.org/language/details3/sq-AL_details.xml', '', ''),
(46, 3, 0, 'Hindi', '', 'pkg_hi-IN', 'package', '', 0, '3.3.6.1', '', 'http://update.joomla.org/language/details3/hi-IN_details.xml', '', ''),
(47, 3, 0, 'Portuguese Brazil', '', 'pkg_pt-BR', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/pt-BR_details.xml', '', ''),
(48, 3, 0, 'Serbian Latin', '', 'pkg_sr-YU', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/sr-YU_details.xml', '', ''),
(49, 3, 0, 'Spanish', '', 'pkg_es-ES', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/es-ES_details.xml', '', ''),
(50, 3, 0, 'Bosnian', '', 'pkg_bs-BA', 'package', '', 0, '3.4.8.1', '', 'http://update.joomla.org/language/details3/bs-BA_details.xml', '', ''),
(51, 3, 0, 'Serbian Cyrillic', '', 'pkg_sr-RS', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/sr-RS_details.xml', '', ''),
(52, 3, 0, 'Vietnamese', '', 'pkg_vi-VN', 'package', '', 0, '3.2.1.1', '', 'http://update.joomla.org/language/details3/vi-VN_details.xml', '', ''),
(53, 3, 0, 'Bahasa Indonesia', '', 'pkg_id-ID', 'package', '', 0, '3.3.0.2', '', 'http://update.joomla.org/language/details3/id-ID_details.xml', '', ''),
(54, 3, 0, 'Finnish', '', 'pkg_fi-FI', 'package', '', 0, '3.4.2.1', '', 'http://update.joomla.org/language/details3/fi-FI_details.xml', '', ''),
(55, 3, 0, 'Swahili', '', 'pkg_sw-KE', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/sw-KE_details.xml', '', ''),
(56, 3, 0, 'Montenegrin', '', 'pkg_srp-ME', 'package', '', 0, '3.3.1.1', '', 'http://update.joomla.org/language/details3/srp-ME_details.xml', '', ''),
(57, 3, 0, 'EnglishCA', '', 'pkg_en-CA', 'package', '', 0, '3.4.6.1', '', 'http://update.joomla.org/language/details3/en-CA_details.xml', '', ''),
(58, 3, 0, 'FrenchCA', '', 'pkg_fr-CA', 'package', '', 0, '3.4.4.3', '', 'http://update.joomla.org/language/details3/fr-CA_details.xml', '', ''),
(59, 3, 0, 'Welsh', '', 'pkg_cy-GB', 'package', '', 0, '3.3.0.2', '', 'http://update.joomla.org/language/details3/cy-GB_details.xml', '', ''),
(60, 3, 0, 'Sinhala', '', 'pkg_si-LK', 'package', '', 0, '3.3.1.1', '', 'http://update.joomla.org/language/details3/si-LK_details.xml', '', ''),
(61, 3, 0, 'Dari Persian', '', 'pkg_prs-AF', 'package', '', 0, '3.4.4.1', '', 'http://update.joomla.org/language/details3/prs-AF_details.xml', '', ''),
(62, 3, 0, 'Turkmen', '', 'pkg_tk-TM', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/tk-TM_details.xml', '', ''),
(63, 3, 0, 'Irish', '', 'pkg_ga-IE', 'package', '', 0, '3.4.5.2', '', 'http://update.joomla.org/language/details3/ga-IE_details.xml', '', ''),
(64, 3, 0, 'Dzongkha', '', 'pkg_dz-BT', 'package', '', 0, '3.4.5.1', '', 'http://update.joomla.org/language/details3/dz-BT_details.xml', '', ''),
(65, 28, 0, 'RokSprocket Module', '', 'mod_roksprocket', 'module', '', 0, '2.1.9', '0802', 'http://updates.rockettheme.com/joomla/138/b61e70db', '', ''),
(66, 28, 0, 'RokGallery Extension', '', 'mod_rokgallery', 'module', '', 0, '2.31', '0802', 'http://updates.rockettheme.com/joomla/286/21ffe006', '', ''),
(67, 28, 0, 'RokBooster Plugin', '', 'rokbooster', 'plugin', 'system', 0, '1.1.15', '0802', 'http://updates.rockettheme.com/joomla/287/cb577720', '', ''),
(68, 28, 0, 'RokAjaxSearch Module', '', 'mod_rokajaxsearch', 'module', '', 0, '2.0.4', '0802', 'http://updates.rockettheme.com/joomla/290/1d5a0af1', '', ''),
(69, 28, 0, 'RokWeather Module', '', 'mod_rokweather', 'module', '', 0, '2.0.4', '0802', 'http://updates.rockettheme.com/joomla/292/a0cbba72', '', ''),
(70, 28, 0, 'RokStock Module', '', 'mod_rokstock', 'module', '', 0, '2.0.2', '0802', 'http://updates.rockettheme.com/joomla/295/87c1121c', '', ''),
(71, 28, 0, 'RokFeatureTable Module', '', 'mod_rokfeaturetable', 'module', '', 0, '1.7', '0802', 'http://updates.rockettheme.com/joomla/296/fb9111b3', '', ''),
(72, 28, 0, 'RokMiniEvents3 Module', '', 'mod_rokminievents3', 'module', '', 0, '3.0.2', '0802', 'http://updates.rockettheme.com/joomla/297/1686051690', '', ''),
(73, 28, 0, 'RokQuickCart Extension', '', 'com_rokquickcart', 'component', '', 1, '2.1.4', '0802', 'http://updates.rockettheme.com/joomla/298/ddfa10eb', '', ''),
(74, 28, 0, 'RokPad Plugin', '', 'rokpad', 'plugin', 'editors', 0, '2.1.9', '0802', 'http://updates.rockettheme.com/joomla/299/e07875c9', '', ''),
(75, 28, 0, 'RokBox Plugin', '', 'rokbox', 'plugin', 'system', 0, '2.0.11', '0802', 'http://updates.rockettheme.com/joomla/301/dfc993d8', '', ''),
(76, 28, 0, 'RokCandy Extension', '', 'rokcandy', 'plugin', 'system', 0, '2.0.2', '0802', 'http://updates.rockettheme.com/joomla/302/2df8a4e2', '', ''),
(77, 28, 0, 'RokComments Plugin', '', 'rokcomments', 'plugin', 'content', 0, '2.0.3', '0802', 'http://updates.rockettheme.com/joomla/303/d1fd7b76', '', ''),
(78, 28, 0, 'RokSocialButtons Plugin', '', 'roksocialbuttons', 'plugin', 'content', 0, '1.5.3', '0802', 'http://updates.rockettheme.com/joomla/381/269989291', '', ''),
(79, 50, 0, 'RA Images', 'Set up Ramblers Images for J3 web sites', 'ra-images-media', 'file', '', 0, '1.2.0', '', 'https://raw.githubusercontent.com/ramblerswebs/updates/master/updates/raimages.xml', 'http://www.ramblers-webs.org.uk/', ''),
(80, 52, 0, 'Ramblers Library', 'Rambler Library for J3, walksfeeds etc', 'ramblers-manifest', 'file', '', 0, '1.3.0', '', 'https://raw.githubusercontent.com/ramblerswebs/updates/master/updates/ramblerslibrary.xml', 'http://www.ramblers-webs.org.uk/', '');