There seems to be a hole in the bottom small portion of the door between the sliding door and the static portion of the door. This leads right into the house and creates a huge space for air and other things to get in. What would be the best solution to fix this? I have called the manufacturer but it will take a while for them to get back.
Normally on the rear of the sliding portion of the door is a flap that engages at the last moment as the door closes. That may cover your gap. If you don't have one, you can add it (search for "sliding door draft stopper").
But looks like you could cut a block of wood to fit the gap (or, fancy, 3D print it). The strip insulation is available at most hardware stores.
But really, this looks like a manufacturing defect, not even an install defect.