Hello. Welcome to Just Answer.
Is the outlet functioning correctly... both when something is plugged in, and when you press the TEST button?
Reverse polarity wouldn't change the functionality of the indicator light. In addition, I don't think GFI outlets will work at all with reverse polarity.Some brands are set up so that the indicator is lit only when the outlet is tripped, to let you know it's tripped.This is because a popped out RESET button isn't always visually obvious.