Anyone having issues booking Jetstar reward flight from Tokyo to Melbourne?

Hi, I’m trying to book three Jetstar business flights Tokyo to Melbourne. They are on the website but when I go to pay I’m taken to the Japanese site. It all works fine until I go to pay. Then they won’t recognise any of my credit cards. I rang Qantas and they said there weren’t any reward flights available on that date (December 26) even though I can still see them as being available.
Does anyone know what the problem is?