Did you buy Assassin's Creed 3 (PC) from the Ubisoft Store? If so, you might be struggling to use an Xbox One controller. The keys are mapped all wrong. I found the
Assassin's Creed III - Wikipedia
Assassin's Creed III - PCGamingWiki PCGW - bugs, fixes, crashes, mods, guides and improvements for every PC game
Assassin's Creed 3: Maus-Tastatur-Steuerung nur halbherzig implementiert?
Assassin's Creed 3 Remastered coming at the end of March - Polygon
Unable to Change Keyboard or Mouse Control Settings AC3 Remastered Archives - PC Mac Help Blog!