I have noticed that some hotels have rates that you can not use points for, or that you can book only if you have the breakfast option.
Can you book a random date in another location apart from where you have tried. ?
I booked in the UK a few days ago using points, and tried a dummy booking in Limoges and had no problem.
The web site should show "
ALL benefit. Use your Rewards points to receive a discount of at least 40€."
Look for the two small coin icon next to the room type. Example shown above.
The point reduction offer is at the last stage of the booking process, as testman has already said.