[TYPO3-english] Cannot activate extension in extension manager

[Martin Braun]

Hi all,

I've been looking for a solution to this problem allover the web but couldn't find anything.

When clicking on an extension in extension manager it is not activated but the list is reloaded 
and the extension remains inactive. When installing a new extension from TER it becomes visible
in the extension list but remains inactive.

I'm running Typo 6.1.9 on Ubuntu server 14.04.
I did not run any installation script but copied the installation files (filesystem and database) directly from another machine
and imported the mysql-dump via phpmyadmin.
I've checked that:
- typo3conf and typo3conf/ext directories have owner www-data:www-data and have access rights 775
- LocalConfiguration.php has has owner www-data:www-data access rights right 664.

Is there any way to debug this problem any further? no error messages are displayed

thanks for your help,
Martin