Cache Issue

That actually is not a cache issue, but a memory issue jester69.

WordPress (the core), your theme and your plugins all need memory to be able to work. Your PHP is currently configured to work with 128MB of memory but your site (wp core + theme + plugins) needs more and Autoptimize sadly was the last one to request memory (71 bytes, in the function that clears the cache-dir). The fact that you can’t activate (guess you have a similar error) is consistent with this problem.

The solution will either be to set a higher memory limit in your wp-config.php or to consider removing one or more plugins (possibly after looking into memory usage as described here).

hope this helps,
frank