Originally Posted by Maelstrom

Firstly, make sure that the rate you are booking has the "coin" icon, which indicates the rate is eligible to be booked with points. Some prepaid promotional rates, unfortunately, do not allow points to be used.
I have been able to make two reservations this past week on rates that have permitted the redemption of points at the time of booking online - one was a prepaid rate, the other was a flexible one.