Update: I found a web app for OCC so I went ahead and installed it.
I was perfectly able to run commands through the interface (which is a terminal-like interface that runs inside of NC). The only issue I had was that I had to edit the .conf file to exit out of maintenance mode.
So I guess the problem of not being able to run OCC commands has been partially solved. Frankly, I’d rather run them in my own terminal, so if anyone has an idea of why this is happening, I’d be happy to hear about it.
EDIT: Turns out the web app isn’t happy about running db:convert-filecache-bigint which is one reason I’m trying to make occ work, in the first place :-/
Thanks for your replies so far!