Rainbow Six Siege Purchased on Steam Shows "Ownership Cannot Be Verified" on Ubisoft

I purchased Rainbow Six Siege through Steam, and as expected, the game launches via Ubisoft Connect. I registered with Ubisoft using the same email address as my Steam account. However, when I click the "Launch Game" button, the game fails to start and displays the message: "Ownership of this product cannot be verified."

Previously, I had no issues playing the game. Despite purchasing it through my Steam library, Ubisoft now claims the game is not associated with my account. This is incredibly frustrating, as I have paid for the game and can no longer access it. I request Ubisoft to resolve this issue immediately and restore access to the game linked to my account. This situation needs urgent attention.