Reach out to Hyatt Gold Passport here on flyertalk. I checked and they are selling standard rooms for cash.

So unless this is one of their one or two blackout dates for the year, they should allow you to book an award. The phone agents usually won't be much help because the cash room is not available for the Hyatt Daily Rate so it shows unavailble to them for awards and they don't know the rules well enough to push the issue.

This has happened in the past and in the case where it wasn't one of the very limited # of blackout nights at the hotel HGP has been able to take care of getting it booked.