3600482 - OAuth 2.0 Password Credentials Flow fails with "User authentication failed: Unauthorized"

• The OpenID connect application in Identity Authentication Services (IAS) is configured to generate SAML assertion for SuccessFactors.
• While calling IAS endpoint /oauth2/token with the username and password, an error message is encountered: 

{
    "error": "invalid_grant",
    "error_description": "User authentication failed: Unauthorized"
} 

SAP Cloud Identity Services

invalid_grant, User authentication failed: Unauthorized, Unauthorized, User Authentication, OIDC, OAUTH2, SAP Cloud Identity Services, IAS, SAML assertion, SuccessFactors, Login Name, Logon Identifier, Allowed Logon Identifier , KBA , BC-IAM-OID , OIDC/OAUTH2 component in SAP Cloud Identity Services , Problem