Acrylic domed skylight. A: Lost seal. B: Condensate trapped between the inner and outer done. Likely someone caulked/sealed where there should not have.
Needs replacement. Nicely flashed curb.
Explain to your client, within the domed skylight aluminum inner frame, much like a window frame, there is an angled channel to disperse condensate, then the seal, atop an outer extruded aluminum frame. Incase of seal ware/failure, as in your case, condensate is dispersed to the roof.
Acrylic domed skylight are inexpensive compared to manufactured galvanized sheet steel and glass HIP or Gable Skylights.
Acrylic domed skylight life expectancy, 5 to 10 years. Average Cost, no installation, $1,000.00
Galvanized sheet steel and glass HIP or Gable Skylights, 50 years. Average Cost, no installation, $2,750.00.
I use to fabricate sheet metal skylights, as well as flashing, coping, goosenecks, drain flanges, crickets, during the winter when I was BUR roofing when I was in my early 20’s when work was slow in preparation for the coming year. If my memory serves me well, 12 and 13 bends to fabricate the rib and top rail. All manufactured from 8’ x 4’ foot minimum 26 gauge, at time 24, galvanized sheet metal passed through roller cutters and bent on hand breaks. All joints soldered.