1992 suburban tailgate

My '92 Sub has a button on the dash that you push sideways to release the top tailgate latch, that releases OK but the top tailgate does not pop open. Someone has to be back there to lift it up while I hold the button over, I thought it should open slightly so I can walk back without taking the key out of the ignition and opening it from the outside. The gas cylinders are strong enough to hold it all the way open. Does anyone know about this? Thanks.

The latch mechanism needs to be cleaned and lubricated, or replaced. Remove it, clean it, lubricate it. Or replace it. It's no more complicated than that. 25 years of service is pretty good. It's time for some TLC.