I use Minecraft both on Nintendo Switch and on a tablet:  there was no way to join another player's world. Two days ago I downloaded the new upgrade 1.16.221 and also my friends did. When I try to enter my friend's world on multiplayer with a friend who is online, I get the message "Could not connect to world". My friends use Minecraft on PC with Windows 10 or Xbox.  If I invite my friends they can join me in my worlds. I have a Nintendo Switch online annual subscriptions and on both I have a confirmed Microsoft account: why I can't play with others? On my Android tablet I don't even receive any message of invitation. It's so annoying!