Performed the steps outlined here,
Jtech Laser Diagnostics Test - FAQ / Laser - Onefinity CNC Forum
My conclusion is the driver in the laser body itself has gone bad, since I tested the input to the laser and it is correctly(?) adjusting from 0 to 5V when OF controller sends M5 vs M3S1000
Will contact JTech support tomorrow and report back.
Update: Contacted support and they sent a new laser which solved the issue.