Why is my subscription pending on communities hosted on ither instances?

I’ve just made an account here to lighten the load on lemmy.world/support my home instance. My email verification came through straight away (unlike when I previously tried to sign up a few weeks back) and I was able to join local communities without problem. But when I try and join communities on other instances I just get “subscription pending”. These are really large communities which people from here must have joined so I’m a bit confused. Is this a feddit issue or an issue with the host instances? Thanks!