What is the preferred method for Contingent Workers to apply for positions?

We have Contingent Workers who are applying for positions within our organization as external candidates. When they apply, they receive the error "We couldn't update the personal info of this candidate. Contact the customer's help desk." This happens when they apply with the personal email in Oracle, or by using a separate personal email not in the system anywhere.

The contingent workers this is happening to do not have access within Oracle so applying as an internal candidate is not possible.

We have checked the box for Contingent Worker is External Candidate and run the process, Classify Contingent Workers in Recruiting. These contingent workers continue to receive the message and continue submit applications.