Hello and Thank you for choosing Just Answer.
Before I can help you, I will need to know:
The light doesnt come on at all in 4 high or 4 low and you hear no sound or shifting.
I'm Chris, Thanks for allowing me to help you here on Just Answer.
Different expert here
Since the light is not even coming on when selecting high or low this concern is a faulty shift motor on the transfer case. This is very common and there is even a TSB for this concern.
If this helps please reply and say" I accept Chris" so the correct expert gets credit.