1996 Chevy Blazer Question about the hatch

Random question about a 96 Blazer that was just given to me. The hatch won't open.
There is a button to the left of the steering wheel that you are to press so the hatch will open up.
This car had a new engine just put in it -- the hatch worked before then. Now, when you press it nothing happens.

Any way to fix this? Is it a fuse, perhaps?
I tried to open the hatch manually, but it won't let you do that either.

Will be frustrating if we can't open the hatch on an SUV :) ha ha

Thanks!