After implementing the Siebel Connector (18.104.22.168.0) on OIM 22.214.171.124, fail to provision Siebel Account unless the user is under organization 'Xellerate Users'.
Cross-checked everything, it fails because the Pre-Populate Rule - 'Siebel Rule' is 'Organization Name == Xellerate Users'. Anything pre-populated attributes in Siebel Process Form using the 'Siebel Rule' are not able to be pre-populated if the user's organization is not 'Xellerate Users'.
The fix is to use 'Default' Pre-Populate Rule instead of 'Siebel Rule' for all pre-populated attributes in Siebel Process Form.
Shared this solution to Oracle and you can find it via My Oracle Support - Admin User Out Of Organization 'Xellerate Users' Fail To Provision Siebel Account (Doc ID 2231147.1)