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Red alert sensors prtg



Hello, we installed a new firewall in our environment, after this migration, the sensors of our lanes turned red and it is giving the error "It was not possible to establish the connection (code: PE015)" maybe there is some port that I need to release in our firewall to reestablish this communication?


Yours sincerely,

Jean Sanabi

prtg snmp wmi

Created on Mar 17, 2023 2:28:39 PM

1 Reply



Hello Jean,

We have seen the error (code: PE015) more likely related to WMI reporting an issue.

The best approach at this moment will be to understand what is the problem the sensors are having. Could you provide the following information:

-Is the problem happening with all the WMI sensors or just some sensors?

- Do you use the same WMI Windows User Credentials for all the Windows machines being monitored?

- Is there a firewall or antivirus in between the PRTG and the target device that may be blocking WMI?

- Please send a full screen screenshot of the sensor Overview tab.

- Please send a full screen screenshot of the sensor Settings tab.

- Please send a full screen screenshot of the sensor Log tab.

Please use our WMI Tester (https://www.paessler.com/tools/wmitester), run it on the PRTG Host (or host of the Remote Probe) and scan against this particular target, usually the "OS-Query" from the "Advanced" Tab of the Tool works best, please send us the Results.

Please also see our extensive WMI Troubleshooting Guide: https://kb.paessler.com/en/topic/1043-my-wmi-sensors-don-t-work-what-can-i-do

Regarding the WMI user access, make sure the password is the same, also the windows user have to be included in the user groups "Performance Log Users" or "Performance Monitor Users", "Remote Desktop Users" and "Distributed COM Users". You also need to enable permissions and services.

This has been discussed in our knowledgebase, so you might consider to check out the feedback of PRTG users and additional hints here:



And you can get some more information here:


We have seen cases where an user is created with exactly all the admin rights in the correct groups and still doesn't work. But when using a local administrator user it works fine. Even with all the same exact access and permissions.

If all this has been tried and the WMI sensors are still not working, there might be an issue at the windows level with the target device, you can refer to this guide for more options https://kb.paessler.com/en/topic/3713

Note For a list of ports that PRTG requires, please see the article Which ports does PRTG use on my system? https://kb.paessler.com/en/topic/61462

Also, please check the article How to connect PRTG through a firewall in 4 steps. https://www.paessler.com/support/how-to/firewall

I look forward to your reply.

Created on Mar 23, 2023 2:13:54 AM by  Ivan Escalante [Paessler Support]

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.