MyChat Client error #0021: you cannot register this nickname, it is already in use
"Debugging and troubleshooting", "List of MyChat Client errors", "Error #0021".
Error
Error #0021: you cannot register this nickname, it is already in use
Error description
There is a prohibition for a nickname duplication in the server settings. It turned out when registering a new user that a user with the same nickname already exists on the server.
Problem solution
Choose another nickname for a user or disable checking for nicknames duplications on the server.