It’s a bug, I have been able to tap it and hit Subscribe again and it works after a couple seconds.

Pretty sure it’s a bug. Some of the smaller instances I’ve subscribed to show “subscribed” right away. The larger instances seem to show pending, but as far as I can tell it works as expected.

Seems to be a bug, I think it happens most frequently when trying to subscribe to a community on a busy instance. It doesn’t seem to affect functionality though, I see new posts, vote and comment, etc. Sometimes if you refresh the page or try again it goes away and says subscribed, but I wouldn’t worry, doesn’t seem to change anything right now. Just assume it means subscribed. I think for this community right now it says “sub pending” for me actually.

It takes a few seconds to subscribe since the server is limited to a finite amount of interactions per refresh. Give it like 30 seconds.