3360571 - Corporate IdP initiated SSO failed in IAS with error "User authentication failed.null Id" in IAS troubleshooting log

It's a SAML 2.0 Corporate IdP initiated SSO scenario.
Login error occurred in IAS.
Identity provider cannot process the response due to wrong configuration. Please contact your system administrator.
In the IAS troubleshooting log, there is the following error.
User authentication failed.null Id...

Identity Authentication

Identity Authentication 1.0

SAML, corporate IdP initiated SSO, IAS, null Id , KBA , BC-IAM-IDS , Identity Authentication Service , Problem

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