Contingent record does not appear in duplicate search results

Summary:
Trying to merge a duplicate candidate record with their existing contingent worker record. There are no hits coming up on the Check Duplicates option even when using the exact information of the Contingent Worker record.

Content (please ensure you mask any confidential information):

I have an active contingent worker that has applied for a position using their personal email that was not on their contingent record, resulting in a new candidate record. I am trying to use the Check Duplicates function on that new candidate record to merge this new record into their existing contingent worker record so that we can avoid any issues before creating an offer. However, when I click Check Duplicates, no matches are found — even with the exact name, person number, email, etc. The search does not return the Contingent worker.