Do you have measurable voltage forward?
Remember, measurable voltage is milliamps.
I have seen it (often) where due to wiring deficiency midstream, measurable voltage was present but amperage to light the bulb insufficient.
I even had one stubborn customer who refused to concede this point, and rather than allowing us to rerun the wire from switch to bulb insisted we only replace the damaged portion ... so we went back, 5' at a time, through a 40' something boat, until we could find enough clean and clear electricity to illuminate the bulb. Only then did he realize he'd just spend 10x in labor what it the wire from the beginning would have cost. Sometimes it's not efficient to "find" the actual problem, but better to just say it's in this wire somewhere and it's not in the new wire ... so pull away!