most of those even though they are push button 4 wheel drive, they still work off of a vaccum. you need to have a local auto mechanic to take a look under the front end where the vaccum lines attach to the transfer case and see if they are unplugged or if there is a defected one.
there are many things that could potentially be wrong with your case. can u engage your 4wheel?
It may have the original transfer case that was recalled
It could be the shift motor on the T Case. Or it could be the automatic shift button switch on the dash.
If the button is not working, might be a vacuum line problem. Vacuum lines engage the 4x4, might need to check the lines to the 4x4 transfer case.
The 4wd in the 1999 Chevy blazer is electronic, you just have to push the button. If you have pushed the button and it doesn't engage, it might be a vacuum line. The lines are made of rubber and over time they melt. It costs about $25 for a new metal line. Also, the 4wd is under the battery. If you take the battery out, you might notice that a line got disconnected accidentally.
check vaccum lines on differential or by shift linkage
All that you do if put the shifter in the four wheel drive position.
the transfer case motor has to be replaced
Probably low on freon.
check the vacume lines that go to the front dif
put trans in neutral and put 4wheel in gear then go to drive in stop mode only
transmission won't engage when you push the button on john deer 155c automatic