For some reason obtaining CPU utilisation information via WMI can be somewhat trickier than any other WMI data.
The bottom line is that, if it works using an enabled administrator account, then you have a permissions problem.
Some of the following may work:
- Add the monitoring user to the performance log group
- Enable the administrator account (normally only applies to Windows desktop Operating Systems)
Also, try the following FAQ article – How do I setup the Windows User for wmic