Sorry to hear that you are getting this authentication error.
This error usually occurs when you are using an account the game was not originally activated on.
Please ensure you are signed into the correct Ubisoft account in Ubisoft Connect. If you are and the issue is still happening, please contact us directly.
You can contact us via a private message on our social media channels here:
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Alternatively, you can reach out to us via a support ticket ... Read more