Do U have a Max Air roof vent cover over the vent that leaks? I had this situation. I found that when I removed the MaxAir cover it stopped leaking. The cover is mounted by drilling holes into the sides of the vent rim. I had resealed around the vent as you did. I inadvertantly built a 'Levy' of lap sealant around the outside of the vent edge and when it rains there was a little lake or mote of water all around the vent that got deep enough to leak into the drilled holes for the MaxAir cover.