I have the same issue as this guy at https://github.com/itchio/itch.io/issues/763.
I cannot buy the game via paypal.
Contact email@example.com if you are still having problems with your purchase.
The staff at Itch handles all the payments/downloads, hopefully they will be able to help.
(I already use the preferred payment method mentioned in the link)
i will contact the support. Still doesn't work.