Can’t update my profile

Then you will need to change your Username to something different.

This is a consequence of the community migration from GetSat, which allowed multiple users to have the same username to Vanilla that requires all usernames be unique. In order to not break user accounts resulting from the migration, it allowed username duplicates to be created, but will not allow them to remain if you change (update) your profile.

This is noted in the Message Board post: Some comments related to editing your profile