Username contains invalid characters

[darkwolf123]

Hello, i need help. When i try to connect to the server, an error message appears "Failed to connect to the server" and then "the username contains invalid characters" .
What can i do ?
Thanks

 

[Chriss]

Have you tried making the resource pack to prompt?

 

[darkwolf123]

Yes...it gives the same message.I'm running version 1.12.2

 

[Chriss]

What version were you using?

 

[Linds]

Does this happen on all servers you try to join or just Potterworld?