I just noticed this warning when trying to access my forum (which is self-hosted):
"We're sorry, but a temporary technical error has occurred which means we cannot display this site right now.

You can try again by clicking the button below, or try again later."

I didn't make any changes on the site today. What might have happened? What/where should I look for a fix?

I get the same error when trying to access the gallery.

Yesterday I occasionally encountered the same problem.

It looks like you may have items on your site that are not compatible with PHP 8. Please try recovery mode, as described here

https://invisioncommunity.com/4guides/welcome/getting-support-r292/

Thanks.

I have no idea how it happened, but as I checked on the server, the PHP was reverted to 7.4 (instead of the 8.0 it was at). Getting it back to 8.0 solved the problem. Now to figure out why it changed!

No problem. Glad to hear you are back online.