Windows NPS “The revocation function was unable to check revocation because the revocation server was offline.”

By | October 15, 2018

Today I decide I would add another Windows 2016 NPS server at our other datacenter for some redundancy. When I was doing my testing I got the following error.

At first I thought it was an issue with our offline root CA. For troubleshooting I turned the offline root CA. Hmm still getting the same issue. So I started looking at our sub certificate authority. After lunching Enterprise PKI mmc I saw the following. CDP Location #1 and #2 are saying “Unable to Download”

I fire up my web browser to go to and get a 503 from the web server. Hmm that strange…. Next place I decide to check is Internet Information Services (IIS) Manager. All web sites are online.  Next I browse where the crl files are located.  Everything looks to be ok.

After confirming the CRL is correct I restarted IIS. After restarting the IIS I could not get to load. Last thing to do was reboot the server. Sure enough after a reboot the server everything came back online. I hate to be that guy “Have you tried turning it off and back on” but this time it seem to resolve the issue.



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