Same for me,first time it happens with any purchase on Itch, and there are no other purchase options. Big shame, I was about to buy it on Steam then I chose for here because I also get a DRM-free copy (and the devs get a bigger cut), but if they can't fix this I'd rather hold off for the time being.
Hey guys, we are very sorry for the inconvenience! We had a problem with our Pay Pal account and we were not notified. We've extended our holiday sale an additional weekend to make up for the error. Thanks for reporting the problem!