Diesel Gas Lock off Solenoids not Opening

I have a Diesel Gas Australia sytem which uses Lovato equipment fitted to a 4.2 Diesel Patrol ute . I have established that the lock off solenoids are not opening and by apply power direct to the solenoid I have established these both work. By applying power to the tank shut off solenoid power source at the tank end I have established the integrity of the wiring back to the solenoid in the engine bay. There is power at the cab on off switch so the issue is between the switch and the shut off solenoids.

Something is not allowing power to get to the shut off solenoids as I was wondering if anyone could pass on some troubleshooting ideas. I am just dealing with the wiring but I can appreciate others would advise me to wait until a technician can look at it some time after Xmas but I would like to hear some ideas on what to check or a explanation on the wiring path as I am not sure whether something else is holding back the power supply. The wire to the brake from the switch I can see is still connected and I assume that would send a message to shut the gas off when the brake is applied