What is the error message in the event viewer?
Currently, there are no errors NPS is generating. We did have a Type 18 error which has been fixed. The keys are verified as matching in IAP and WS2012 NAP.
When did this problem start happening?
The problem became pronounced August 2-3 when a couple Windows 10 devices would not connect.
What CA issued the server certificate on the NPS server?
No external CA was used. The person setup an internally generated certificate.
Try unchecking "Validate Server Certificate" on the Windows 802.1x supplicant.
Not sure where to do this at in NAP. I will be looking.
Seems like there are 2 wireless policies. Seems odd, but I did not set it up.
See screenshots attached of RADIUS configuration on WS2012.