That metal piece is normally just snapped into the patio track. In the video, we show one made of vinyl which works the same way as yours. Also take note that for some vinyl patio doors, the active door can be removed from the inside of the house by adjusting the wheels up into the door and lifting up the door. That may be the case for you, as well, but I'm not sure.
It may be a trick of the picture, but your door header looks lower in the center. That could be the problem. Every door track I've seen in California has been the same height inside and outside. your cap on the outside makes it hard to tell.