I'm level 28 swashbuckler with level 27 companions.I have tried to the best of my ability to do all the quest. Now for some unknown reason I have only one quest left and it is in Port Royal and of course I cannot get in. I have gone back and checked over every city and cannot find any quest that I missed. I have run out of options. Ready to give up and go home lol.
Looking at your quests, it appears you might have missed picking up the next quest after Coils of the Serpent from Sister Snake on the Isla de los Muertos. Head back there and let me know if that helps get you back on track. If there isn't a quest there for you, the best thing to do would be to contact customer support and have them help you get back on track!