It is pre molded seamless and waterproof polyur.
Anderson skylight window leaks.
Then lift it off and keep it to one side.
Original installation squareness.
I also see water stains on the bottom of the wooden window frame suggesting there has been wind blown rain or snow melt leakage too.
Anderson rep said seal was defective.
Two years later after a downpour one of the other skylights developed a leak.
Our new anderson skylights leak.
Unscrew the fasteners holding the cover of the skylight window on with an appropriately sized driver.
Leaks at skylights left unattended can lead to costly structural damage rotted roof sheathing rotted roof framing and wet moldy insulation as well.
Then press down on the roofing shingles to seal them tight.
They leaked brand new.
I think your anderson slider window has more than air leaks.
Start by checking that the windows are basically square in the frame.
With a scraper slowly remove the weather stripping around the skylight cover and the curb.
At the time of installation 3 years ago our contractors had a anderson rep out to replace seals in 4 or 5 of our brand new skylights.
Take a moment to seal any cracks you find on the cover with the clear silicon caulk.
1 lift up the shingles next to the skylight one at a time and brush out any dirt and debris.