Hey I am testing my website's checkout system with a test product. I am excluding tax for it just to avoid confusion. I enter all the pseudo-info (shipping info etc.) and when I click the 'make purchase' button I get the following error:
SetExpressCheckout API call failed. Detailed Error Message: Security header is not validShort Error Message: Security errorError Code: 10002Error Severity Code: Error
Any help would be MUCH appreciated.