We recently removed the option to purchase a gift code with Paypal in response to a greatly increased number of fraudulent transactions. We are working with Paypal to find a long-term solution, but unfortunately do not have an estimate on when or if this payment option will return.
Our players can help us combat fraudulent purchases by code re-sellers by only purchasing Minecraft gift codes from Minecraft.net.
In the interim, you may wish to try a different payment option. We are actively working to make many popular payment options around the world available to our players. We apologize for any inconvenience.
