So my sonicwall 3600 went down. Sonicwall sent a replacement. I uploaded the saved configuration into the replacement and didn't notice any problems.
The next day, users say they can't access the VPN. After a half day talking to Sonicwall support, we figured out that users cannot access the VPN using their UPN as they used to on the old 3600 but can access it using their SAM.
L2TP / IPSEC with RADIUS (NPS) authentication. Funny thing is, the RADIUS server shows success (reasoncode 0) with both the UPN and SAM. Sonicwall's "Test" area in RADIUS shows Success when testing with UPN.
Thanks in advance!