Resealing any port from the outside will only be a temporary fix at best. It is necessary to remove the port, clean up all the old sealant and rebed the lens.
It is unusual to see frameless ports held in place by bolts or screws. One of the issues with screws and bolts is the differential expansion rates of the acrylic and the steel. This causes the lens to crack. When screws are used to bed the lens, they are typically used outside of the lens, not through the lens, to hold the lens in place until the sealant cures.
Dow 795 or 3m High Bond Tape are used to secure the lens. This is a 2 step process. First the lens is bonded to the cabin side and then a second layer of sealant is applied to seal the outside edge of the lens. There is a good set of videos on Andy Miller's YouTube channel, Boatworks Today on installing frameless ports. He uses the 3m tape and Dow 795.