In Portal for ArcGIS 10.8.1, an administrator cannot add an AD user to the group if another built-in account exists based on the same e-mail.

Workaround

• Add another administrator to the group.
• Log in with the original Portal for ArcGIS administrator account, retrieve the password from the password storage system, and add the AD user to the group. Log out from the administrator account and log in with the AD user again.

Steps to Reproduce