Client setup: Sonicwall NSA 4600 and NPS on Server 2016.
Error: RADIUS Authentication Failed (MSCHAP error: E=649 R=0 V=3)
Tried just about everything to fix this one. Gradually unpicked every single bit of security right back to clear password and nothing seemed to work.  In the end I went into the user’s account and under ‘Dial in’ changed the setting from ‘Control access through NPS Network Policy’ to ‘Allow Access’.  Finally I’ve had a successful authentication attempt for my test user.  Now I need to start dialling back up the security setting by setting and try and get to the bottom of what is going on.