Not the best place to ask but generally make sure your connection is working properly, that you a have Uplay account, and if it is downloaded you may need to see in store purchase for the online or the key may be bad.
Ac unity just sucks, there are many glitches and it's not worth your time. If you are a fan of the assassin's Creed games, I would recommend sydicate, it's my personal favorite. If you like those kind of mechanics in a game, try far cry 4, this game is so good and I can't stop playing
Thanks! Your answer is awaiting moderation.