Minecraft PE multiplayer, invalid name?

I was playing minecraft on my tablet and my little sister tried to join, but it said invalid name, I tried to let her join on my moms tablet but it said invalid name again, so I let her try on my phone (which shares the same info as my tablet) and it worked, but she refuses to use my phone so I need to know how to fix the game, Please Help!

If there's commas or dashes in her name then she needs to take them out or delete them off her name. You can't have commas or dashes or dots i don't think numbers can be in your name neither. So yeah, tell her to put only her name no dashes, underscore, commas or symbols in her name. Tell her to put only her name in the name box on mcpe. Try that & see if that helps.

3 of us the family loving mine craft, just did the update and now we can't re-join each other's world, it says invalid name. Only one of us had a symbol in the player name, got rid of it, but no improvement. Any other suggestions?

Well, as soon as I posted the question above, I went back into the game and was able to join one of the others. The 3rd person is still locked out, maybe we haven't given it enough time yet?

Me and my friend both got the new update and after that we played multiplayer. The next day we were going to play multiplayer again but my friend changed her name it said invalid name we changed her name back to how it was in the beginning but it said invalid name again. What do I do?

I try getting on a Minecraft server with my friends and it said

You can only have letters no spaces or any symbols

Th at does not work

I tried deleting the letters and spaces in mine and my friends names and it works perfectly but for a server i needed to ad numbers how does that work?

What if you have deleted all the spaces and dashes and you have no capital letters and it still doesn't work what do I do to fix it

Mine isn't working. I can't even type in my name. What do I do!

This is a lot of help and it works

I tried to join my bff game and it said invalid name. I tried changing her name and it still didn't work. She can join my game. None of the names work that we tried. What do I do?

None of these work and it never works on my server either, this helped with local worlds though! So thanks for that but it won't fix for the server, ITS JUST THE ONE PERSON TOO!