Backglass install problem

That lock strip should begin and end in the lower center. There is a special tool to install or remove it.
Get in the back seat and work the gasket and glass further into the bed while someone else is applying pressure along the top from the outside. I did this same chore last summer. I feel your pain, HOT HOT HOT !
!Honestly, I could still see 3 of the teeth in the upper right corner radius when I decided close enough. Good ol' gravity has since closed the gap further. That's where the problem is though. The glass is a little high and/or a little far out of the car still.