I am having an issue with a report with RLS on the service.
The implementation is very simple using an access rule table with 2 columns [Username] and [Company] governing the Company view in the report. Then the dynamic RLS is implemented with a LOOKUP to that table looking for a matching USERPRINCIPALNAME().
My testing does work as expected in both local and service for all the defined users, but one.
The filter rule does fail for this user only on the service.
It seems like this user were an admin able to override any RLS rule.
But after extensive cheching, it tourned out that this user is not present anywhere I can check.
It's not a member of the report workspace, less than having any edit permissions.
It's not a member of the linked Sharepoint/Teams groups.
It doesn't show anywhere, but it can skip RLS.
Any hint would be GREATLY appreciated.