For me, if you are choosing a different instances for your alt account, always have a look at the instance’s server location info and their blocked list, just in case

Not always. I’m not typing so fast.

Have you tried to log out then log back in again? I heard that it may because the JWK token changes or server update recently

For me, all lemmy.world communities I subscribed was totally blocked on my beehaw.org account, so I create another account on lemmy.world.