There is always the possibility that you may have more than one Ubisoft account so please be sure to check any other Ubisoft accounts you may have.
1. Start by launching the Uplay PC client
2. Click the Account Avatar at top right then select Log out from the list.
3. Login with a different Ubisoft Account / Email Address.
Steam: Games purchased through Steam will appear in the Games tab in the Uplay PC application. If you are trying to play a game originally purchased through Steam, you can either launch the game through the Steam application or through Uplay.
If you have just purchase your game and if your activation key is already in use, please contact your retailer.
If you need help checking which account your key is registered to, please contact us, we will be happy to investigate further. Please include your game's CD Key / Activation Code when submitting a ticket, it will help our support team to provide you a better and faster assistance.