If the RADIUS Tester is reporting a time-out communication error as shown on the screenshot below:
Try the following troubleshooting steps:
1) Verify that the computer/server's IP Address where you are sending the request from is correctly defined as a RADIUS client on the server where the NPS and the RADIUS plugin are installed.
2) Verify that the RADIUS client has been defined using the IP Address as the server uses to see the client.
3) If you have a firewall between the server and the client, check if there is any rule preventing the communication between them on ports 1812, 1645, or the ports you have defined for the service.
4) Check if the server and client are using the defined ports for communication. You can query this from the NPS MMC console, right-click the NPS main node, and select properties. Click the Ports tab to verify this configuration.
5) Verify that the Mi-Token AD LDS and the NPS services are running:
6) Verify that the RADIUS client is enabled - in the NPS MMC console, open the RADIUS clients folder, open the properties for the defined client and check the settings tab:
7) Check if the Windows Server's firewall allows the communication for RADIUS requests. The following Powershell command enables it:
Get-NetFirewallRule -DisplayGroup "Network Policy Server" |where DisplayName -like "*RADIUS*" | Set-NetFireWallRule -Service Any