eSignature name validation failed

Summary

Candidate is getting a esignature error during eoffer acceptance

Content

We have configured esignature in Taleo Onboarding for eoffer acceptance. The signature type used is First Name. The candidate is using his first name for esignature. However he is getting a "The action cannot be completed."Confidential Information - FirstName" signature validation has failed."Confidential Information - LastName" signature validation has failed" error.

Kindly let know possible reasons for this error.