Turboprop Engine not starting in cold weather

I’m working on a turboprop aircraft, and I’m encountering an issue in which
the engine does not start if ambient temperature is below -5 Fahrenheit (NG is
stuck at 16). As soon as the temperature is increased over -5 Fahrenheit, the
engine starts normally. Any clue what may be the issue?

The Grand Caravan starts at -40C. So I suggest using this engine.cfg and
testing and once working then slowly update until you figure out what setting
is causing the issue.