When I subscribe in a community in another instance it always says "pending " in yellow. I can comment but I am not officially subscribed to the community. E.g. subscribing to “[email protected]”
Maybe I just need to wait.
Edit: It says “subscribe pending” in yellow
for communities on other instances (that are federating with your home instance), search (from your home instance) for !communityname@domainname
that works, most of the time. otherwise it’s a federation replication issue or a bug.