I'm trying to book a day's car hire in France for next June using my Hertz points online. I have more than 10,000 yet every variation I try comes up with the message that I don't have enough points.

Is it not possible to book in France or is something else going on? I've never tried to use the points before so don't know the limitations of this scheme, although everything I see on their website indicates that this should be possible.