[Grumpy old man]

I do these all the time by myself , did you Mark the center on both the frame and glass ?are you starting from the bottom ? What size cord are you installing into the gasket to pull it in ? For the inexperienced installer it helps to have 2 helper one on each side of the truck providing downward pressure and maintaining the glass on the center line ,use lots of window cleaner as lube and I it will drop in easy peasy ! Less than 20 minutes . The glass and gasket have to move down at the same time don't attempt to push the gasket down onto the flange and then make the glass follow it , with downward pressure evenly across the top a glancing slapping motion down provides persuasion .