There seems to be lack of understanding on how circuits work, so I'll start with some basics. DC power starts at power-source, goes through load and comes back at ground of source.
Every complete circuit has two segments, power and ground. Now if you've got break in power segment, which you yourself have identified as problem, there's absolutely
nothing you can do on ground circuit to fix it.
Until you identify location of break in power circuit, there is no way this bulb is gonna light. You can spend next 300-hrs checking ground circuits and even if there's problems, fixing them will not fix broken power circuit.
I'll draw up diagram of power circuit and identify test points since text isn't describing it properly.