How do you get Rogue to start on steam? I pressed "play"and it keeps going back to "start" Is there any way of resolving this issue?

I bought AC Rouge on Steam three years ago, and it's asking for a CD key now. I don't see the key in my library, and I'm a bit lost. I've already activated the code on purchase but now its asking me for it again and i cant find it. Can anyone help me?

So this and unity are both full scale ac games and I feel like unity completely overshadowed this one. And I find it super strange because unity had a massive controversy when it was released since it was ultra buggy. I have remembered Unity all this time (and quite fondly) and I literally just got reminded this game was a thing after almost 10 years....

So thanks to Uplay being shut down years ago, I can no longer access my account in order to play rogue, I've since made a new connect account with the same email, but now the game tells me it failed to authenticate ownership, am I screwed? If so, I'm never buying a ubisoft product ever again. Any help would be greatly appreciated....

The game does not start! In general, I buy the game and start downloading it, that's all downloaded, I click on the "Play" button. And it doesn't start, it just doesn't start, there were no errors, First comes the "Download-Cancel- and the Play button comes out again" I have already searched everywhere for the exact answer and have not found a solution to the problem....