I've started playing the entire Assassin's Creed saga again, however in AC1 I'm having some problems. In the assassination missions, you need to scale a tower and synchronise viewpoints in order to see your objectives and further your progress in the game. However, I've already scaled all of the towers and synchronized all of the viewpoints, so it's impossible for me to see any of the objectives! This has happened in all of the poor districts, so I can't see any objectives on the map, only "help civilians".
Is there any way to solve this? Or do I just need to start the story again?