Candidate can't apply as the system states their email already exists IRC-1590024

Summary

Candidate receives message: A candidate with the same email already exists. Supply a new email or perform a search to find the Candidate associated with this email (IRC-1590024)

Content

We have a candidate that is trying to apply to a position. He keeps getting this error:  A candidate with the same email already exists. Supply a new email or perform a search to find the Candidate associated with this email (IRC-1590024)

Most of the time we see this error because a candidate applies multiple times but when we look this individual up we can not find him. I am unable to search for candidates by email address so I cant find if someone else out there is using this email address.