I've already checked every point of the bus. They all seem to test fine. Any other ideas?

 

I think it may be the USB controller? When I unplug the fiber optic from the USB controller I can see the fiber optic lighting up. I don't see it on any of the other points in the MOST. The problem is I'm afraid to pull the fiber optics out of the harness because there's no clip holding them in.

 

The other optical cables can be removed from their harnesses by removing a little tab on the harness. The usb controller has no such tab. As such I am afraid to pull the cables out of the harness.

 

Unless the cabling was fiddled with…. I’d confirm that the source voltage and amperage is adequate for the device, first.