Be sure to distinguish between the two promos. The one in the OP (Hampton) has been around for a while and you might have read about/tried it before. The Doubletree one I noted in post #3 appears to be new and behaves differently.
Both promos require app authentication, so you should have received at least a pop-up dialogue. If you didn't, it could be that your browser blocked it, and therefore you never saw the authentication request.
Anyone who gets a rejection message should check their TopGuest account (if you might have one) to see if it is still active.