I'm hoping someone can point me in the right direction on this. I have a site, upgraded from Joomla 1.5 to 2.5 to 3.8.6 that runs on the JA Teline 3 template. The owner does not want to upgrade to 4 or 5 right now. I have updated the template files to the current version available on your site. It runs fine when the hosting account is set to run on PHP5.6 but when I switch it to PHP7 I get the error

The file Cache Storage is not supported on this platform

The back end will load but nothing else. If I switch the template to Protostar the site loads fine

In the back end when looking at the system folder info everything is writable under 5.6 but on 7 everything turns red and is unwritable. I have at least a dozen or more other Joomla sites running on this server using php7 with no problems. Any idea what I might need to do or check here?

I have confirmed that all files and folders are owned by account:account and not account:root or something wierd. This is the same ownership that I see on all of the other working php7 accounts on the server. I have used Akeeba Admin tools to verify and fix all the file permissions.

Is there something in Teline 3 that would cause this error? It goes away if I switch to protostar or something else.

I should also mention that for a time we had the site running fine on a PHP7 account but it is only since updating the site recently to the most current versions that this error has started occuring. The URL provided is a temporary testing URL so feel free to look and poke around if needed.