3+ night award stays unavailable online?

I'm trying to book a 4 night award stay at the Hilton Waikiki Beach, but the booking system keeps telling me that award certificate stays are unavailable for my given dates. I tried searching while not logged in and the site displayed the normal rate of 40k points per night. Once I log in to book, I get the "unavailable" message. The same room is available for 1 & 2 night stays, but not 3+. I also tried using the flexible date search and the property shows no 3+ night availability for the next 12 months (as far out as the search would go). 1&2 night stays were available throughout the 12 month window. I replicated these results with other cat 6 and 7 hotels in the area.

Is this a glitch in the system that others have experienced? Can this be remedied by calling customer service?

Thanks for the help.