C3500 w/DM0 passes audio but none of the meters are showing level, including the LCR output meters. Any advice is greatly appreciated; big conference happening this week!
What troubleshooting have you done? I assume you have power cycled everything? Make sure you are turning the DM0 on first and allow it to boot fully before you attempt to power on/connect the Surface.
Post Fader metering? 
That would be too simple to fix.
Got an emergency call once from my club where it was exactly that. The guy thought nothing is coming into the board and hasn’t pushed up a fader once. 
I have had that awhile ago occasionally. Rebooting the DM would fix it. It just happened to me again yesterday.
Submit a trouble ticket.