I have been trying to add a user to an AGO account with Enterprise Login enabled. The Enterprise Login is configured to automatically add users upon successful login.
When I try to add a new user via logging in for the first time, I get an error
Unable to assign user 'UserName@DOMAIN_org' to this account 'xxxxxxxxxxxxxxxx' , Username is not available
I have verified that this user's email address is not currently in my Organization's users. Also, I am able to successfully log into the IdP endpoint with the target user account.
Any suggestions on how to diagnose this issue and try to make this username available to the org?