I'm implementing Express Checkout in PayPal.
I have no problem with the first two steps, SetExpressCheckout
and GetExpressCheckout
. But when I use DoExpressCheckout
, I encounter the error "Security header is not valid".
The API credentials are the same!
I've fixed it by changing the $environment
to live
in DoExpressCheckout
. (The difference $environment
makes is that it'll use https://api.sandbox.paypal.com/nvp/
instead of https://api-3t.$environment.paypal.com/nvp
)
But why?
Is there something wrong with https://api-3t.$environment.paypal.com/nvp
?
https://api-3t.sandbox.paypal.com/nvp requires different user-accounts than what https://api-3t.paypal.com/nvp requires.
The sandbox accounts can be activated at developer.paypal.com