Unable to connect the world, the world is no longer open

Today I play Minecraft with my friend. And then it shows this screen to us. It said that unable to connect the world, the world is no longer open. My friend and I don't what happening. Our versions are same. It also is Minecraft BE 1.20.51. And our internet connections also are Ok. I try to use computer to connect the my friend's world and my friend is using Switch to create the world, and then we can't play multiplayer games. But I can play it with my other friends use computer. So I want to know what is the problem?