Hello,
Here are a few things to consider:
1.Have you tried to click the verify button next to the IP address?
2.Ensure that there are ere are no network issues and firewall rules blocking the RADIUS traffic between the access point and the NPS server. Ensure that AP is online, reachable from RADIUS. According to Configure NPS UDP Port Information | Microsoft Learn "The port values of 1812 for authentication and 1813 for accounting are RADIUS standard ports defined by the Internet Engineering Task Force (IETF) in RFCs 2865 and 2866. However, by default, many access servers use ports 1645 for authentication requests and 1646 for accounting requests"
3.Examine the NPS server logs for more details on the error.
Regards,
Karlie