"OCI External Access Synchronization" erroring when setting up 1st RCM user access certification

Summary:

setting up 1st RCM user access certification and trying to configure non-fusion data source for OCI, believe I've done correctly and the connection is testing ok… when sync process "OCI External Access Synchronization" it is failing, but can't see any log file/error message for ESS processes "External Access Sync" and it's "Dependent Job"External Access Sync"

Any ideas? has anyone got it working as expected?

What group does the newly created dedicated OCI user account need to be in? and the roles for the Fusion ERP per_user account that match by username?

Found the oracle documentation but little on the setup needed on the OCI side.