That Name Isnt Available

After capturing our first Pokémon the app asked what name would you like the other trainers to call you?
We tried so many times and each time the app would inform us "That name isnt available".

Wished tech support could amend this.
Rated it two stars because it worked with the first Pokémon but cannot use the app again.

oki doc about Pokémon GO, v1.39.1