Multi-Player not working in realms

I have a realm. I've had the realm for a while, years I think. In our house, we all play multi-player in the realm from a single Nintendo Switch device, again - we played multiplayer on the realm for years, from one single device.

After the 1.21.62 update, I have not been able to play multi-player in my realm, only single player. When I try to join as a player 2 the screen splits, it starts to load, and then it goes back to single player / full screen.

Other friends of mine that I have invited to the realm are able to join, no issues there. However, they are joining from a different Nintendo Switch.
I am up-to-date my switch and my minecraft game Ver. 1.21.62
I can play multi-player on all other games, including minecraft but ONLY in regular worlds, not in my realm.

I have a video of the issue if that is helpful, let me know how best to send.