Have the same problem. Bought Joom SEF adsmanager extension and gets this error: Fatal error: Class 'sef_joomsef' not found in /.................

Well i don´t have adsmanager but am resurrected that is built on adsmanager (the same extensions works) Even tried a modification. Eitherway I get the error above.

Joomla 1.522 PHP 5.3 JoomSEF free version.

Have downloadID 65b6...

Version Info
Installed version: 3.9.4