Hey there, Unattacked. If I'm understanding properly, you're having trouble playing Siege on PC. I'm not seeing the game license on your account, so this would be the reason you're unable to launch the game. Have you recently purchased the game from a digital store such as Steam, Epic or the Ubisoft store? If so, it's possible the permissions for the game ended up on a different account.
You mentioned playing on Xbox - could you let me know your Xbox GamerTag?