I was transporting a transmission and dumb *** me didn't think it needed to be strapped down, so long and behold a sudden stop made it roll and when it rolled back it slammed right into the tailgate. From that point the hatch wouldn't open, I'd hear the actuator go but it wouldn't unlatch. After a week of searching online I found 3 forum posts on multiple sites saying the same and with people graciously thanking them. Well maybe they changed something mid gen but in my 2000 Blazer 2 door it did not. In the process I did figure out how it should be done and luckily I only broke 2 panel pins in the process, only because I started the wrong way.
First of all you wanna make whatever room you can back there, 4L60E + "300lb man" + "trying to fix hatch" = "Breaking the window seems like a good solution"
Take a 15mm open box wrench, the smaller the better, and unbolt the latch hardware from the glass. You'll be able to access the 2 bolt heads from each side of the hump. This is tedious but yanking back on the panel til it pops does not make it much easier and you'll just break the pins. Now you can open the glass.
Now it's time to get the latch out, good news that's done from the outside. Take out the small screw on the top left of the hump. Now gently push on the panel until you hear a couple pins pop, as long as you don't go He-man on it you should get 1-2inches of clearance without breaking any of the panel pins.
Behind, and slightly below, the latching mechanism you'll see a piece perpendicular to the latch and makes an L with it. Take a flat screw driver and push down on it at the joint. Once that pops the glass side of the latch will release and now you can open the tailgate.
The hard parts done, have a smoke and/or drink a beer if you hadn't already been doing that. With the tailgate open you can now take out the 2 screws on either side and finish popping the panel out. Now take the hex screws holding the inner panel and remove it, carefully because the actuator is mounted to it.
Now if the actuator needs to be replaced, the only replacement I found was through a dealership for about $60. If it's fine and it just wasn't engaging you can buy the Dorman 42426 Rear Window Actuator Kit
which is an improved hook up than stock.
Hope this saves someone from the headache I had figuring it out