Cannot join friend

When I try to join my friend who's also on mobile bedrock it loads for a very long time and then gives me codeword “kelp“, I've already updated Minecraft and my friend has multiplayer on, but it won't let me join still. No mods installed either. All I have to do is accept his join invite and it'll load and then tell me codeword “kelp“. It should let me into his world but it doesn't.