4wd problems

[4ballin]

For some reason last night driving home in snow she was perfectly fine in 4wd and then when i turned off the shifter switch 4wd would not re-engage when i turned it back on.No light indicating 4wd in dash as well as no 4wd at frt wheels.What controls kicking in the 4wd on a 98' limited?Does anyone no the chain of command on that so to speak.It starts at the switch and goes where?Its snowing so i need to cure this problem asap!Thanks guys.