May Patch Tuesday introduced an issue when applied to Domain Controllers using NPS or RRAS.
Microsoft last week released some out of band patches which you need to apply, to DCs, if they are affected by this months paches.
The company released the following cumulative updates for installation on Domain Controllers (no action needed on the client-side):
Microsoft also released standalone updates:
More info on BleepingComputer: https://www.bleepingcomputer.com/news/microsoft/microsoft-emergency-updates-fix-windows-ad-authentication-issues/