Same thing is happening to me. If I switch switch users I can play but lost my online account/purchases (because they're on my main account) which no longer works and crashes upon opening. I can't play anymore with anything I paid for. I can only start a new world on a new switch profile without any of my purchases or saves.
I've been receiving the same issue - over the past week it was crashing more and more. It's gotten to the point the game doesn't even open anymore. The game just crashes as soon as I open it.
The only fix I've found is changing my Nintendo Switch profile. But - All my purchases and achievements are gone, so that's not much of an option. I haven't been able to play for the past 3 days.
I have 2 portals. One in the nether. One in the overworld. They should connect automatically.
I understand if I had multiple portals to connect them to each other but I have one portal only. It should go to the nether and come right back - I shouldn't have to figure out how to link them. They have always linked automatically. Thank you for your feedback, I appreciate learning a fix so I can fix my current world at least.
But this is definitely a bug considering they should automatically connect to each other. I've never had this problem until this world I just created.