The left panel is where everything happens in the cab, it contains the processor that communicates with the main controller in the chassis. Of course there can still be a number of causes, but still the first thing you need to verify is that the left panel is getting power, especially when you put it under load such as powering it up. I had another Bobcat , at that main plug you found, pins and sockets were clean and good, but when I probed the power wire going into and coming out of the connector I found I had power on the input side, but nothing coming out, wire connection was bad where it was crimped inside the connector housing. Another jumper wire around job and got it running. The wires you need to check would be wires numbered from 1000 to 1999, they will be red, red/white, or red/orange. And you'll have to test the wires by probing them, once you unplug a connector you can't test when powering up the controller. Pull the left panel out and start testing those wires I mentioned, and do when you power things up at the right panel as well. Again, all the right panel does is send input commands, such as start, back to the processor in the left panel, and the right panel gets its power from the left panel. If your wires test good, possibility that the processor in the left panel is going south, but no way I know to test this.
BTW, at any time when you power it up do you hear three short beeps from the alarm or see any message, such as "INPUT", in the hour meter display?
