I revoked the local admin privileges of the account PRTG uses to monitor our servers out of the local admin group, and went through a couple tutorials to setup WMI access for non-administrative users. I'm successfully monitoring performance (CPU/memory/page file), disk space, and even processes with WMI sensors, but I can not get the WMI Service sensor to work.
I granted the WMI namespace permissions at the root so it's not a namespace issue, when I use WMI test to query "Select * From Win32_Service" as an admin account it works, but as the PRTG account (which is granted access to DCOM & WMI) it does not work. UAC is also disabled on both the PRTG server and it's target device.
I'm guessing there's an additional step beyond the WMI configuration to get this one working (for example to get Disk Space on non-system drives I had to grant the user read access to the root of the disk otherwise it wasn't included in the results from WMI) I just can't find anything documented online.