From your post it sounds like you made a booking and then called in to use the certificate. You should not do this, you should call in and tell them you want to make a reservation using your club upgrade certificate and they will contact the luxury services team to complete the booking and attach the certificate. I haven't had many issues with this when I call 1-800-542-8680. Some agents will insist that you cannot combine the $100 credit with the club upgrade even though the rate exists, but that's the only issue I've hit.

If you're asking them to do the booking and this is the response you're getting I'm not sure what to tell you as this hasn't been my experience at all and I booked with one of these in the last couple of months.