Originally Posted by
adventurous
Should I take this to mean that I cannot use the recently-acquired 50% off cert. for a reservation that I already have?
For instance, I have a reservation at a hotel that has no more vacancies--so the certificate is pretty much useless in this case as I understand now.
Correct. SPG50 has limited vailability, and not all hotels offer them either. The fact that the hotel in question is already sold out means that it is impossible to change your reservation to SPG50.