OK, you've wiggled the wires with no result.
With the bars to the right and the ignition on, are all the front lights, instrument and dash lights on?
With the run switch on an you hit the start button does the starter relay click?
Do you have a 3 amp charger? Can you charge the battery? Are all the cells to the full mark? O'Reiley's can load test it. And they have an AGM motorcycle battery for 85 bucks. I just had to replace mine.
After that it's back to tracing wires one by one for an open or short. All black/yellow should show ground.
If I recall, you don't have a meter just a continuity light. There' a way to use that but it's nasty! 8~)
Velorex 562 sidecar w/trunk
Headlight power switch
Manual fan switch
Blue wire mod
Yellow wire mod
Voltmeter relay wired
Coils direct wired w/relay
extended foot shift
extended brake pedal