If the ballast is okay, it is your switch or bulkhead connector. The Ignition 1 12V on the dark blue wire is gone. Easy to check with a meter. Ignition 2 on the brown wire is present, that is why it starts.
Craig

2014 Ram 1500 Laramie, 73 Cuda
Previous mopars: 62 Valiant, 65 Fury III, 68 Fury III, 72 Satellite, 74 Satellite, 89 Acclaim, 98 Caravan, 2003 Durango
Only previous Non-Mopar: Schwinn Tornado