I have an 83 and I cant find this button on the upper hatch that allows you to open it. Do you have a picture? I might just be missing it.You should be able to open the upper hatch from the inside. there is a button that lets you open it up (at least there is on the FJ60). If it's the tail gate that won't open, then the post above correct. There is a lock on the right hand side that can be pulled up to unlock.
edit: why do you have solenoid actuated door lock on an FJ60? Are they aftermarket?