Subscribe pending? - sh.itjust.works

What does it mean and how do I fix it?

I'm guessing you're seeing this on non-local communities? I think it means you're local server hasn't started copying and caching that content yet. I haven't taken a look at that part of the code yet, so just a guess.
Yep. Mostly lemmy.ml for some reason, yet it's not every community.
Yeah, I have several pending subscriptions on lemmy.ml as well. It definitely seems to correlate with how overloaded the instance is.