What happened when you tried to do the update. Did it show an update taking place?

If i remember correctly, there was a green field with "update successful"
BTW cache cleaning in backand and browser doesn't matter

Ok now there was an update for brezzing forms and Akeeba Backup.
And i got the following warning
JInstaller: :Install: Die XML-Installationsdatei konnte nicht gefunden werden
Hope that is the correct translation
JInstaller: :Install: The XML-Installation file couldn't be found

This must be bad folder permissions or some wrong path for tmp folder

• check / fix folder permissions
• check your tmp / log folder paths in configuration

After doing the above, if you cannot upgrade via the UI,
make a site backup,

and try to extract the Joomla package files into joomla root folder, and then go to "Extensions\Manage\Database\Fix"

Note that if you upgrade like the above
you will need to discover / enable "installer plugins" for Joomla installer to work after upgrade, and also "Install more languages" button will show an empy list ...

Okay thanks, will try that the next days. The permission and folder sounds possible, but the last updates thre update process works flawlessly.
BTW I still receive the emails, that an update is availible

I am closing this at this time as there doesnt appear to be any core bug just a failed update. It can always be reopened if requitred

OK no problem. :)