My friends cannot find my world

1. (I am host with ipad ios 14.2) my friends cannot find my world since 4 days ago i think 1.16.100 will fixed but the problem doesn’t fixed .. ( sorry, I dont know what should I capture what about it )
2. when I go to other server with my cellular data but it said “  you must be connected wifi to play with your friends ( have photo )
3. some worlds of my friend I cannot join, it said “ unable to connect to world “ but when creat new world I can join to my                                                                
                                       I appreciate if you help us. Thank you