trouble with 4 wheel drive shift lights on 2004 Chevrolet Suburban 1500

Everything was fine, when i came out of the store the neutral light on the 4 wheel drive controls was on.I tried to shift to 2 wheel, 4 wheel, the lights would blink as if it was trying to shift. the light blinked for a while then went out. the red light remained on as if in the neutral position. the car still drives as if in 2 wheel and shifts fine. no matter what button i push, it wont get off the red neutral light. any thoughts? thanks, jim