Welcome to House Repair Talk.
If you are having a leak through the top of your patio door, the first place I'd look is the flashing of the patio roof and around the windows. Flashing will extend out over the roof membrane and up your wall and either be covered by siding or terminated with counter flashing in brick walls. The area around the window can leak, travel down the inside wall and the framing of the porch roof will stop the water travel.
If you can post some pics so we can see whats going on, or call a professional roofer to identify the area of water intrusion.