your probably logging in to the wrong Uplay account
contact Ubisoft Support
https://support.ubi.com
Hello Bubka1992, welcome to the forums!
Sorry to hear that you are unable to start your game. In this case, it looks like you are logged into the wrong Steam account, as the game has been originally purchased from Steam. Can you please provide us with your Steam username, so we can check if it's the correct one?