1. Open the file parameters.php located in /app/config/
2. Find the below line and change parameter true to false in
'ps_cache_enable' => true,
or copy and replace the entire line above with the one prepared below:
'ps_cache_enable' => false,
3. Delete prod folder inside /var/cache (don't skip this step !)
Now, You should have caching turned off and the Caching switch should work fine next time.
Good luck !