I had a similar experience a few days ago with a Fairfield Inn in Michigan. Weekend nights unavailable for points bookings, but plenty of standard rooms available.
I called the Platinum number and spoke with a clueless agent - I literally read her the terms 7 or 8 times, and her response was always "I can book you a room with cash, but not points"...infuriating.
I finally asked for a supervisor, who apparently called the hotel and got me a room with points. But there's still no availability online for any weekend night, so nothing really changed.