Assassins creed 4 abstergo challenge?

Im having trouble beating the abstergo challenge with sharing three royal convoys locations. This is because the royal convoy icons are on my map and in blue but there is no timer it just says"gain money: high". When I sail to them there are no ships it's just the icon sitting there mysteriously in the middle of the ocean no ships anywhere in sight. It's been days they have not disappeared and it still says I haven't shared any royal convoys out of three. I also think this is effecting the social chests and whales too because I haven't completed any of those abstergo challenges either. I have 7 abstergo challenges to complete and I cannot complete it because of this I'm pretty disappointed. If you know how to help or what the problem is please let me know. Thanks