Sky light leaking

[Xfitter71]

I recently had my roof re-shingled and the sky light is leaking. I had this problem when it was installed during construction of the addition. That sounded wrong. It leaked after the job was completed. I fought the problem years but re-shingled the roof my self in '97 or '98 and used a lot of that sticky backed rubber stuff and flashed it as best I could. I'm an x-welder but just used common sense not knowing exactly the proper way to do it. I never had another leak till this new roof was done about a month ago. It's leaked every hard rain since. The roofer has been back once and is coming this morning but he says he believes it's the bubble leaking. He adds more caulk and says it doesn't make sense why it's leaking. My thought is , it didn't leak till he did the job. The unit is one with the built up curb, sets a few inches above the shingles. The roof is 5/12 pitch(?) and the ceiling is also pitched but not that much. The leak marks start about half way down and it's obvious to me they follow the sheeting or dry wall joints and the water has to getting under the felt to get to the sheeting to get to the dry wall. Where can I get info with photos or drawings on how to flash it? I can't remember how I did it fifteen years ago. I'm 71 but it looks like I'm going to have to do it again myself to get the leaks stopped.

[HayZee518]

sky light

was the curb a pre-fab unit or was it just a 2x4 construction when the opening was cut in?
were the shingles cut back exposing the sheathing when the curb was put in?
in any case the flashing starts at the bottom and successive layers overlap the previous piece along the sides and roof line all the way to the top.
st the top you start at the top and use one continuous piece and cut it and overlap the sides.
add another full width strip on top of the top piece overlapping about four inches.
for asphalt shingles under butter the last row where it ends about two inches from the curb.
make sure where the nail goes through, there is some compound or it will leak at the nail location.
the sky light should fit over the curb so its flanges over lap the curb.