Robert,
if you have the adjustment on the roller set at the highest point and the bottom clip still won’t stay engaged, then you will need new rollers or as Fred said above, flip the pins over, inside the hollow tubing, to raise back up to original position. The rollers are getting hard to come by, and when you do locate them, they are very pricey$$$. Also, there is a plastic tract on top of the railing, it must be in good condition, or the door will not open/close properly. I believe the plastic tract is also still available. Hope this helps.