3457323 - Not able to open payslip or mashup from EC after enabling IAS

After enabling IAS, when opening payslip, mashup or ECP service from SF, you may notice below symptoms:

1. A pop-up screen appears to logon ECP system , but the access to ECP fails with error  "Client, name, or password is not correct; log on again" even through the ECP user ID and pwd are correct.
2. Below error message can be seen in the SAML 2.0 trace :

• 'Name ID value 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' cannot be mapped to any user alias'
• No user found with alias 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' (format: unspecified). Long text: No user found with alias 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' (format: unspecified).

• SAP SuccessFactors Employee Central Integration to SAP Business Suite
• Employee Central Payroll (ECP)

T77S0, SFEC  IAS, PersonUUID, UUID, PayStatement, Pay Statement , KBA , LOD-EC-GCP-PY , Payroll Integration EC to Employee Central Payroll , LOD-EC-GCP-PY-MAS , Employee Data Maintenance via Mashups , LOD-EC-GCP-PY-PST , EC Payroll Pay Statement , Problem