Water leakage is a common problem with sliding door thresholds.
Sliding glass door leaking from top.
Try to follow where the water will go when it hits siding when it hits door when it hits door frame when it accumulates on the threshold or patio porch deck and see if any of the flow paths by gravity or by wicking along relatively tight interfaces allows entry into the house.
Note that if the sliding glass door leak you described has already worked its way under any adjacent exterior siding you ll likely have to remove and reapply that siding as well in order to install the new material and repair the leaking sliding glass door but the extra effort will be well worth it the next time coastal winds blow rain your way.
Be sure to tape thin sheets of plywood over the glass to protect the door from flying pieces of concrete.
If you have a problem with water leaking it will usually be on the bottom track threshold of the non stationary door.
If you cannot re create the leak problem inspect the interior of the door for stains or rust.
Spray the door and look for the leak location.
A sliding glass door is no better than the frame into which it is placed.
Aim a garden water hose with a sprayer set on mist or low at the outside of the sliding door.
To slide the heavy doors along the metal frames the doors use metal or plastic rollers.
Do you have any leaking windows or doors.
The plugs are usually in the top but if the universal door ge.
Test the door for the location of the leak.
If a frame is crooked water can leak into the gaps between door and frame.
Since sliding glass doors and sliding impact windows are heavy they move along metal tracks fitted to the bottom and top of their frame.
Have a reputable sliding door contractor remove the door if it has not been damaged build a new frame and reinstall the door.
Sometimes water intrusion is severe staining carpets and causing dryrot at the subfloor baseboards and sometimes even the wall.
There are 2 drain plugs in the bottom of a universal sliding glass door one on in each corner.
I used this tape for sealing.