I booked 9 nights, finishing up just about an hour ago (combination award and paid). Checking now, though, I get:
Unexpected Error
Unfortunately our booking system was unable to process your reservation request. Please try again.
If you have any questions about your reservation, please call 1-800-633-7313 in the United States and Canada. For international contact information, select the Hyatt Contact Numbers link.
It's just coming up on 0200 Omaha time on a Sunday morning which would seem to be an ideal time for web site maintenance.
Have you tried a Twitter message? I did that earlier this year when it was about 3 in the morning and they answered immediately.