Phorum has gone south

I have a phorum here (URL removed due to spambots).
All that’s being served is the template code. Everything else (including html wrapper code, etc.) is not.
I don’t know how to proceed.
I could have sworn phorum was a one-click install at some point.
I ssh’ed in and did ‘php index.php’ and saw the same template code being output. No errors, etc.
I did the sanity check through the admin panel and everything says it is okay.

This has been working fine for a few years, so I’m at a loss.

Any help appreciated!