Your fiber optic MOST communication line is open circuited. Each module on the MOST bus has a repeater in it, if any module fails then the signal is not repeated and the bus goes down. Most common point of failure is the Bluetooth module that sits on the top of the electronics stack in the left rear electronics compartment. Its the one with that is a small rectangle about an inch tall with one rounded end and the electrical and fiber optic connector on the other. Search on here for bluetooth module and I'm sure you will come up with several dozen posts on how to bypass it, and test it.