Installation broken after php upgrade

Hi, new user here.
yesterday I got an error message that I need to upgrade to at least PHP version 5.5.9 so I went to my cpanel and changed the php version to 6.

After that change I can no longer access piwik. No server error. The page just doesn’t load.

Do I need to do anything else with the mysql database via cpanel?

Side issue - my wordpress installation on the same main domain is fine except for the visitor log on each post is no longer counting anything.

Any help or ideas welcome.