"I bet' it's the old "you didn't jumper the ballast terminals."
Use a meter or a light and see if you have power BOTH to the "big red" and to the "small red" WHEN CRANKING using the key to activate the starter
You MUST jumper the ballast together so that the brown wire is included
HOW THIS WORKS
During "run" that ignition "run" voltage (called IGN1) is supplied by only one switched wire into the engine bay, usually dark blue. This wire branches off and depending on year/ model, supplies ignition, voltage regualtor power, alternator field, and smog doo-dads if used and electric choke if used
THAT VOLTAGE GOES DEAD DURING STARTING
Ignition "full battery power" is supplied during cranking by a separate contact on the igntiion switch, called IGN2 feeds out, usually brown, into the engine bay and connects to the coil+ side of the ballast. This must be incorporated/ jumpered to IGN1 for any ignition not using a ballast resistor
