Rebuild Performance Counters

If nagios was working OK and then suddenly you get lots of errors similar to :

UNKNOWN - The WMI query had problems. You might have your username/password wrong or 
the user's access level is too low. Wmic error text on the next line.
[wmi/wmic.c:196:main()] ERROR: Login to remote object.
NTSTATUS: NT_STATUS_ACCESS_DENIED - Access denied

You may need to rebuild the performance counters on the machine that cannot be queried.

This is detailed on https://support.microsoft.com/en-us/help/2554336/how-to-manually-rebuild-performance-counters-for-windows-server-2008-6 but to summarise:

Open a administrator CMD window

To Rebuilding the counters:
     cd c:\windows\system32
     lodctr /R
     cd c:\windows\sysWOW64
     lodctr /R

To Resync the counters with Windows Management Instrumentation (WMI):
     WINMGMT.EXE /RESYNCPERF

Stop and restart the Performance Logs and Alerts service (only if it is running)
Stop and restart the Windows Management Instrumentation service (this should always be running)