If you can lift the rear hatch open manually and it stays open, the struts are good.
If it's really heavy, or doesn't stay open after you lift it full open position, the struts are bad. (The struts are responsible to provide the main lifting force. If they fail, the motor will sense the overload and stop any attempt to life the hatch.)
If after you initiate an open procedure, you hear it unlock and hear the motor try, it may be the body control module may be out if sync. (If may actually forget how to open after unlocking.) To fix this possibility, disconnect the negative vehicle battery cable, and step on the break pedal for 30 seconds (drains the residual currents from the capacitors in the modules.) Leave the battery disconnected for another 10 minutes. The body control module will reset.
If after the latch unlocks but you hear no motor, its possible the fuse has blown. Think it's #7 in the fuse panel located in your engine compartment. (2013 Edge). If ok, then suspect the liftgate motor itself; or a wiring problem. The most likely location of a wiring break is the yellow wire that located in the rubber boot that connects the body to the hatch.