If you are unable to activate the AccelerateWP Site Optimization Module from the AccelerateWP dashboard, chances are that the error message already provides a hint about the problem.
For example, the error might be something like this:
AccelerateWP: End user can't activate "Site Optimization Module" - Found conflicting plugins: Unknown
This means that a plugin needs to be disabled which in this case, the plugin is labeled as "unknown".
One of the probable causes we are aware of is due to a previous cache plugin.
While the plugin might be removed or disabled, it still left some files in the user's directories.
This of course will conflict with AccelerateWP suite auto-generated files and thus create the error you are seeing.
To solve this issue, just look for leftover "advanced-cache.php" files within the wp-content directory of the WordPress installation.
Removing and/or renaming the file will allow enabling the module.
