@TTV-b894781603 Hello! Welcome to Ubisoft Discussions! I'm sorry to hear you're getting an authentication error. This error usually happens when you are logged into a different Ubisoft account than the one your Steam copy of the game was originally activated. I suggest making sure you're logged into the correct Ubisoft account that has the game activated. If you are sure that you're logged into the correct account, then we'll have to continue assistance through your Support ticket. We'll be able to gather more information there so that we can take a closer look into it.
I understand you have been waiting for a response back from your Support ticket, and I apologize for that. Our teams are currently experiencing a high volume of contacts, so our response times have been longer than usual. Rest assured, we will send a response back to you as soon as possible.
If possible, I recommend submitting your launcher_log.txt file to your Support ticket since it can help us see what is potentially causing the issue.
Thank you!