1991 Chevy Silverado Front wheels no longer engage

Stuck in the mud and snow last week, engaged the floor shift 4x4, the 4x4 light flickered on, it engaged I drove out, took it out of 4wd and now will no longer engage the front wheels. Transfer case engages both low and high range but not the wheels.
Tried to donate but system locked up, will gladly donate to an address, please let me know what would be acceptable donation.
Dan Leeson