I receive the following response from our offline team:
One thing to check is that access controls does affect what replicas you see. You can only see your own replicas, so whatever user account was used in runtime to create a replica, you need to use the same account to view the replicas in rest calls. I recall the role matters too, so I think "admin" has extra powers and see all replicas for an AGOL service?
Let me know if that helps or not.
Mark