Unable to sync returning user from AD

I have a employee who was in ServiceDesk then left the company and has now returned.  A new AD account was created for him, but it will not sync with ServiceDesk.  If I use a different email address it will create the user and show up.  If I use the email address that he had when he was here the first time he will not show up as a user. 

If I use a different email then sync, then go into AD and change his email and sync again he will also continue to show up, but gives error "The specified Primary Contact does not exist in the portal."

Any help would be greatly appreciated.