Can't accept minecraft invite (no error)

I’m having a problem with Minecraft multi player. I have it installed on an iPad. When someone invites me to their game, I can see the invitation pop up and then I can tap it and press "Accept". But the dialog box just disappears and nothing further happens. No error message shows up, (Just returns to previous screen as if I pressed cancel).

The friend is playing it on an Xbox One.

What could be the problem here?