PHP-FPM Error 500

Short history: I have moved a virtualhost from one server to another with the built in backup & restore.

What I have done: Set the handler to PHP-FPM, instantly receives ERROR 500 on virtualhost's all pages (/roundcube/ too) the site is a Wordpress website. I have tried to delete some content from my htaccess, but not helped. My site is behing Cloudflare and uses https. (But this problem is exists on http too)

I have already tried: a2enmod proxy a2enmod proxy_http

Not helped.

From apache log: [Wed Feb 22 15:02:19.697666 2017] [proxy:warn] [pid 4999] [client 162.158.88.103:19447] AH01144: No protocol handler was valid for the URL /index.php. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule., referer: http://xxxxxxxxxxx/roundcube/

Any ideas? Is it a problem with my configuration or with virtualmin itself?

Thanks!