The alternate payment system, Rixty, is having another RIFT promo offer – For every RIFT purchase you make of $20 or more, you will receive a bonus Spectral Supply Crate (lockbox).
You can make the purchase via the website or in-game using the Rixty payment method.
This offer lasts from 10th July – 31st July 2014.
For further information or if you have any questions, check out CM Ocho’s thread here.
RiftGrate 
Rixty is a piece of junk. Tried to make a payment for about half an hour at which point I gave up because it was never even indicated why my card’s not being accepted. Rubbish:)
Not trying to be condescending (just trying to cover all bases), but have you made sure you’ve enabled javascript for the site? That is often an issue for me when signing up, posting comments/etc on new sites I haven’t whitelisted yet due to having NoScript up.