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

So 2 votes for bug, 2 votes for privacy reasons. I too want to know.

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.

probably the creator of the community want to select who can enter and who cannot, it’s like for private Instagram profile, the owner have to accept your request