I’ve found refreshing my tab won’t change that, but the new sublem (community) WILL appear in my list of sublems on a different page. Maybe a glitch?

Yes

I think the home Server of the magazine is busy/overloaded so it will take a while for the server to process your subscription. But this is purely my speculation from where I experienced it so far.

I’ve seen this a handful of times - unsub / resub ended up working after a couple of tries. That may not be the correct approach, but this platform isn’t great with the concept of error messages yet, so…

All those I joined took seconds. Have you tried refreshing? It might also be that the instance is a bit overwhelmed atm. But, I’m new here so perhaps there are mod only approval communities