I deleted and reinstalled.  This time the installation went very quickly, and lands me at a page with a button to 'visit the gallery'.  But when I click on it, I get the same problem, it just hangs, and says at the bottom of the page that it's waiting.

This is the note from my host: "There is some issue on the site and it is constantly loading.

We do not provide this script and do not plan to offer it.
You can try to delete it and install it again or change the php settings . . .
check the script version compatibility with the php version."

I don't think they are going to give me any more help with it.  So:

Which php version should I be using with piwigo 2.9.5.
Can somebody tell me what other php settings I should be using, if any?

Also, I saw on the forum some issues about time zone settings that might cause problems.  How do I start the local files editor if I can't get piwigo to load anything.

Thanks