Email not Recognized

Hello-

I have a tech who's  receiving the follow message when trying to submit tickets.

“We're sorry, your e-mail address was not recognized by the help desk, so your request for support could not be submitted.

Service Desk”

I checked for duplicate accounts or inactive accounts and didn't find any. It seems to reassociate the account with the old client account, although the emails are different.

Any Idea's Please Advise.