Yaggy97

I have a 2002 chevy Silverado 1500 with the push button style 4x4. The button say it’s in 4wd I can hear the transfer case shift and have checked the front dif dogle and it is working I have 4wd on a lift with no resistance on the wheels and it works but today we got some snow and I plowed my driveway and 4wd did not work at all? Where should I begin?