You need to update pagebuikder

https://www.joomshaper.com/forums/joomla-3-8

Thanks brianteeman.... Solved!!!!
that link talks about "rename the folder mod_sppagebuilder_admin_menu"
I'm so happy!

Having the same problem after updating to 3.8 and I do not have this module (pagebuilder). Cannot access the backend. I get this error:

Error: 0 Call to undefined method JAdminCssMenu::renderMenu()

Any other help?

@Agustin-Pantoja have you read other the Threads to similar Issues?

@Agustin-Pantoja Do you have ssh access to the site?

yes, I have read some similar threads... reading threads for the last five days...
and no, I do not have ssh access to the site. ;-)

@Agustin-Pantoja thanks for Clarification.

Thanks for listening ;-)

Like Agustin-Pantoja I do not have this module (pagebuilder). I read many articles and searched the internet. If any posts are made at all about this error, they are made about Pagebuilder. I do not have PageBuilder installed. Yet I do have "Call to undefined method JAdminCssMenu::addChild()" in the back-end of Joomla 3.8.1. I also updated all extensions etc., before updating from Joomla 3.7.5 to Joomla 3.8.1. Any ideas anyone please? Two sites have this problem. 4 others have not.
In addition. When I rename administrator/modules/mod_menu to administrator/modules/mod_menuold the error goes away, but also my back-end menu. I do see my Controlepaneel (=Dashboard?).

@HanVanHeerde Please create topic on forum https://forum.joomla.org/viewforum.php?f=710

Hi friends,
Having the same problem after updating 3.7.x to 3.8.1 and I do not have this module (pagebuilder).
Cannot access the backend. I get this error:
Error: 0 Call to undefined method JAdminCssMenu::renderMenu()

I did not install SPageBuilder, but the error presented was the same and the solution was similar, in my case, I checked the PHP logs and indicated the error in the 'CCK Module of SEBLOD 3.x', so I had to rename the folder "mod_cck_menu" to "mod_cck_menu_anything" and everything worked again.

Anyone with the same error being presented, I recommend that they see the PHP log file, they will have clarifications on the module that is causing the problem.

This solved my case, I hope it helps anyone who needs it ...

thank you ;-)

Was seblod up to date? If it was it would be useful if you have them feedback

Hi
Yes, all extensions were already updated by auto-update in 'extensions> manager> update', but when updating Joomla the administrator screen displayed only top menu.
The page title displayed the reported error: Error: 0 Call to undefined method JAdminCssMenu::renderMenu()

Maybe I'd better post on the seblod forum,
I'm sorry for posting here.

Then seblod did you no favours by not testing and ensuring their software was up to date and compatible, Joomla 3.8 had a very long release cycle with multiple release candidates that they could and should have tested with

I had the same issue (Error: 0 Call to undefined method JAdminCssMenu::renderMenu()) with a Joomla installation with no 3rd party applications. I deleted the folder "modules/mod_menu" and "administrator/modules/mod_menu" and uploaded a more recent version (in my case Joomla 3.8.2) via FTP and the login is working again now and the error message went away. After that I went to /administrator/index.php?option=com_joomlaupdate and reinstalled the joomla core files (as I still saw some errors in the server logfile). So I assume at least in my case this was caused by wrong update process so its not an issue in joomla itself.

Finally a friend of mine found the problem. The key is to check where is the problem. It has to be related to the menu of the template.
I tried to check the log on the server, but not a clue there. At the end I did point number 5 of this website.
https://www.collectiveray.com/joomla/joomla-tutorials/joomla-blank-page.html
In my case I found out that I tried to override the menu of the backend some time ago, cause it had too many items.
I went to /public_html/administrator/templates/isis/html and there there was a folder named mod_menu. I just renamed it and everything worked out again I could update the website, no problem.
To get rid of the elements in administrator menu/components, better follow this guide:
https://www.joomlashack.com/blog/tutorials/deleted-components-menu-items-remained/

Hope it helps to someone.

Hi, Help me, please, with the site http://www.edu-ungheni.md/administrator/ - HTTP ERROR 500

Please use the forum for support

@inport if needed: forums.

Hi again,

I had another blank page in the administrator backend after updating a different website from the one I mentioned above from joomla to joomla 3.9.2. This time the error was: Error 0 Call to undefined method JAdminCssMenu::addchild

I just checked my own post here and again I renamed the folder mod_menu in administrator/templates/isis/html. Now it works again.

I am starting to think that this is a bug, as I had the very same problem in 2 different websites made by two different developers with different templates and different modules installed.