- Admin console
- The same user address was used as alias in another domain that was removed from the Google Workspace account.
- Sign in to your visitor session using the "Invitation to [Edit/Comment/View]" email from Google.
- In the top right, click your initial.
- Click Delete visitor session.
- Click Send.
- In your email inbox, open the verification code email.
- Enter the verification code in the box provided and then click Next.
- Click the checkbox and then click Delete.
After deleting this visitor account you will be able to restore the recently deleted user.
For additional reference feel free to visit this Help Center article.