06 ML350 TAILGATE WONT LOCK.

I HAVE A 2006 ML 350, TRIED TO CLOSE THE TAILGATE, BUT IT WONT LOCK.  IT WAS MAKING A MOTORIZED SOUND, BUT THAT HAS STOPPED. NOW NO NOISE, BUT STILL WONT LOCK. IT IS CLOSED, BUT NOT LATCHED. THE ELECTRONIC LATCH WILL NOT ENGAGE.  ANY SUGGESTIONS OR IDEAS WHAT THIS COULD BE?

maybe the outside handle is stuck or pulled in the open position??  there is also problems with the latch and or the handle mechanism in the liftgate.  the door usually will latch but just wont lock.