I have been playing around with NPS for a while but today was the first time I had ever set up an Network Policy Service Server on a Member Server in a domain. I then wanted to use it as the Primary Server for Authentication for one of our RADIUS clients but couldn’t figure out why I wasn’t getting Authenticated, I had set it up exactly the same as my other NPS Servers. Checking the Event Viewer I noticed that I was receiving the Event ID 4402 reporting that “There is no domain controller available for domain %1”. A lot of posts out on the Internet were leading me in the direction of DNS issues or Firewall issues but none of these were the issue. I then found this post by Geoff @ UVM and it became very clear what I had forgot to do! I forgot to Register the NPS Server in Active Directory. As soon as I had done that, everything started working as expected!
To Register the NPS Server in Active Directory:
- Open the NPS management console
- Right-click on NPS (Local)
- Click on Register server in Active Directory
I won’t forget that one again!
Until next time!
CTRL F5.me 
Thanks so much! This solved my problem that I was fighting with for a few hours!
OMG, I love you. I’ve been beating my head against this for days. This completely fixed it.
wow can’t believe I had this issue as well! I was looking at ridiculous solutions when it was this all a long! THANK YOU!
wow can’t believe I had this issue as well! I was looking at ridiculous solutions when it was this all a long! THANK YOU!