I have a 2002 Suzuki XL-7 4X4 Automatic.  I have never  taken it off road until last weekend (70K miles already).  It shifts into either 4X4 hi or low just fine, but the front wheels do not have any power to them.  There is nothing turning in the front, even while stuck in the mud.  The green "4X4" on the dash lights up.  I wonder if the front hubs are not locking somehow.   Has anyone on this forum had this issue, and can you please tell me how it can be fixed?  Thank you very much.  Sincerely,  RVADDICT.

Is the drive shaft turning?

First engage the t-case in to high four, lay on the ground off to the side safely yet make sure you can see the front drive shaft and have someone drive the vehicle forward and watch the drive shaft, if it turns the t-case is okay.
These have drive flanges and not locking hubs (like my tracker) so that isn't an issue as they are always "locked".
There is an air pump mounted to the inside of the front bumper on the passenger side of the truck. Check to see if the air pump mounted under the front bumper cover is working or a line is off or with electrical harness plug is full of crap and not connected properly and lastly, follow the lines to the front diff to see if it was tugged off by a branch of something.
This pump causes positive pressure to engage the inner axle disconnect system.
You can pull off one tube at a time an slide a ballon over it to see if it inflates or put some compressed air to it to see if its sticky from not being used often.

The two lines are different sizes to match the size of the barb on the pump so you shouldn't mix them up (okay maybe , I did after my body lift ) and my front "shit-on-the-fly" wouldn't engage.

Hope this helps.

and my front "shit-on-the-fly" wouldn't engage.

Most appropriate way to describe that horrible design.

Thank you very much for the extremely helpful replies.   I will check all of this tomorrow and let you know what happens. 

I removed the bumper and found the pump.  However, here's the problem.  If I have it in 4X4 mode and the car running and in gear, the pump does not run.  However if I disconnect the harness and put 12 volts to it directly, the pump runs fine.  There is a positive lead and two grounds.  If I ground the middle one, it does not run.  The harness sends +12v to the red wire, and ground to both black wires no matter what gear it is in, 4X4 or not.  Might I have some kind of relay out of whack?  The owner's manual does not cover all of the relays under the hood.