It seems to me that in the last few days, if you don't automatically search for 2 weeks around your search period, then it won't give you access to the availability calendars.
It says nothing available. Expand the search parameters, and you find there was plenty available during your shorter window search.
Of course, if you have to search for 2 weeks to see the 5 days you really want to see, then a book it button becomes useless because during a 2 week search, there's always at least one day not available.
Frustrating.