3082307 - User Id Generation failed, candidate is not visible on the Onboarding Dashboard - Onboarding

Initiate Onboarding for candidate from Recruiting, the candidate is not visible on the Onboarding Dashboard. An user validation error is displayed in the BPE Tile:

"We were unable to generate user id. Check your business rules or field mapping configuration and try again."

"Images/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental." 

SAP SuccessFactors Onboarding

We were unable to generate user id. Check your business rules or field mapping configuration and try again., User Id, sequence, rule, user, generation, failed, Onboarding, OBX, 2.0, generateNextEmployeeIDForONB2 with maxTries reached, maxTries reached, GenerateNextEmployeeIDForONB2Impl , KBA , LOD-SF-OBX-RCM , Initiate onboarding from RCM , Problem