Username not allowed on sign up

The username Ana1 is giving me this error. At first, I thought it was the capital A, but if I choose Ama1, it works.

Hi @hernan ,

I tested the username Ana1 and Ama1 in the signup process and could not repeat this error. And there is no error from your tenant logs related to the failed signup.

To check this further, could you repeat this error with the username Ana1 and send the HAR file to me via the DM?