MarketPress checkout is not working.
I’m trying to set up Google and PayPal checkouts both of them look like I have followed the instruction correctly however I get the following errors.

There was a problem setting up your purchase with Google Checkout. Please try again or select a different payment method.
Internal error in server

There was a problem connecting to PayPal to setup your purchase. Please try again.
10002 - Security error - Security header is not valid