This article applies as of PRTG 24

After a scheduled reboot, specific performance counters for a local drive on a server monitored by PRTG Network Monitor stopped working, resulting in the error "Instance(s) not found (code: PE236)." This issue affected only some of the drives, while others continued to function correctly.


You should consider below solutions to resolve this issue.

  1.  Add a Windows Uptime Sensor: Adding a Windows Uptime sensor to the affected device can sometimes help in resolving issues related to WMI sensors. This action forces a refresh of the WMI performance counters. 
  2. Use WMI Tester for Query Validation: Run a query on the device using WMI Tester to check if the specific instances can be accessed properly. This step helps in identifying if the problem lies with WMI access or the PRTG configuration. 
  3.  Check Disk Numbering for iSCSI Disks: For systems using iSCSI disks, verify if the disk numbering has changed after the reboot. Disk numbering changes can cause mismatches in instance identification, leading to the error. 
  4. Recreate the Sensor: If the problem persists, deleting and recreating the sensor in PRTG may resolve the issue by refreshing the configuration and ensuring it aligns with the current system state.


Disclaimer:
The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.