Hi,
This error represents that you have not configured the WMI credentials correctly in OpManager.
To verify that go to the device snapshot page --> Click on "Click here to change" option besides Passwords under Device details --> Select "Use the below credential for the device" and provide correct credential (ex: Username = DomainnameUame, password = password) or select apply the global parameters and choose the correct credential.
Also make sure Test credential works fine before adding the respective WMI monitors (WMI based Partition Details of the Device and Used Disk space in GB).
If the monitored device is OpManager server itself then you need not to provide the credentials , you simply select "Use the below credential for the device" option and leave the username & password blank --> apply.
Regards
Mahendiran.