Hi there Genghis.. welcome to the forums!
When you see the message - "There was a problem authenticating the ownership of this product." This usually means the game is connected to either the wrong Steam account or the wrong Ubisoft account.
Do you have several Steam or Ubisoft accounts?
In order to help you find the correct one you would need to get in touch with us through our support channels as we are unable to ask you personal identifiable information over the forums.
You can contact us here through preivate message or our Ubisoft Support website -
Twitter Support - https://twitter.com/UbisoftSupport... Read more
When you see the message - "There was a problem authenticating the ownership of this product." This usually means the game is connected to either the wrong Steam account or the wrong Ubisoft account.
Do you have several Steam or Ubisoft accounts?
In order to help you find the correct one you would need to get in touch with us through our support channels as we are unable to ask you personal identifiable information over the forums.
You can contact us here through preivate message or our Ubisoft Support website -
Twitter Support - https://twitter.com/UbisoftSupport... Read more