Hard to hear over the fans but it coincides with LEDs on the Panel Unit too so it may be more than one relay.
I short toggled the power to corrupt the image and saw that it reaches the reboot/xstart/istart screen before it does the Connection Board MS LED.
Verify the wires from the TP connector to the Panel Unit. I had an M2000 where some one cut a TP data wire when they were cutting wire ties when clearing old customer wires. The cut was close to the front, underside of the bundle and not in normal viewing. Found it be hooking a spare harness and the TP screen came right up. Mine would come up though because the image wasn't corrupted. If the image had been corrupted, I would have been in a very similar situation except I had spare controllers for parts.