From what I see in the video it looks like the latch releases ok. The gate pops open but it doesn't look like the powered strut turns on to lift the gate up. I suppose it could be a bad "turn on the strut" switch in the latch IF there is such a switch... or it could be the power strut is broken or not getting any power. What I would do next it open the gate all the way by hand and see if it stays up. If it does let it sit for a minute, then push the button to lower it and see if the power strut lowers it. Even if it does or doesn't I"m still not sure how you would know whether it's a problem with the presumptive latch switch, the wiring, or a defective power strut.
Don't have the power liftgate. But my gas struts went bad on my lift gate, the liftgate wouldn't stay up and required 3-8 times more force to raise it than normal. New gas struts and the lift gate lifts on its own after raising it partially with very little effort to raise it to that.
So, pure speculation, but keep in mind the power strut to lift it might be bad, or the other gas strut that provides the spring force to help lift it could be bad. The motor driving it up, probably can only produce so much force and without the spring force of the gas strut to help, can't get the job done.