This has been going on for several months, and I only recent heard of this bug tracker.

I play mainly on my Nintendo Switch, but I have a friend on iPad who cannot join anyone’s games, and no one can join his games. I have another friend on Xbox who cannot join me, but I believe I can join him, and he and I can both join other people’s worlds. It is not the Microsoft account parental settings, as we were all able to play together fine a long time ago, and we have checked our settings multiple times since this issue started. I have attached a screenshot from my Switch attempting to join the iPad.