Minecraft on Switch: We are still working on a fix. However, for a temporary workaround, try not signing in to a Microsoft account. While you won’t have access to servers, Realms, or possibly Marketplace content, you will be able to play single player & split-screen worlds. - HZ
The problem you've described sounds like a temporary issue and should have been resolved now. Please try again, and email us at https://help.minecraft.net/hc/en-us/requests/new … if you're still having the same problem. ^RL