Locate the spring assembly which is often on the top.
Sliding screen door stuck at top.
Determine exactly where the door is sticking before deciding on a remedy.
If the track is bent or squashed straighten it with smooth pliers and file.
If the edge of the door is hitting the frame try tightening the screws on the top middle or bottom hinge on both the door frame and the door being careful not to over tighten and strip the screws.
Find the rollers at the bottom of the door.
Again this is a fairly simple problem to fix.
Just opening or closing the door with too much force can warp the frame.
In some instances the sliding screen door will fall out repeatedly because it is too small.
Most sliding patio doors have one or two small holes at the top and bottom of the door for adjusting the roller height.
First look at the lower track.
The metal frame around the screen door is easy to bend and warp.
If your sliding door is sticking or dragging along the tracks making a grinding noise the springs in the rollers could have become loose causing it to sag.
Your door is old and worn out.
If it fits too loosely in the tracks any vertical movement of the door will cause it to come unseated and it will fall.
Almost all sliding patio doors are adjustable when it comes to height.
Clean it with detergent and water or even a little solvent on a rag.
These hole are often covered with a plastic plug.