Here is the error code
PayPal Express Checkout requests and responses :
sales_apixxxxxxxxxxxxxxxxxxxhttp://www.pcsarticles.com/pp_confirm.phphttp://www.pcsarticles.com/pp_cancel.phpAuthorizationxxxxxxSuccessexxxxxxsales@pcsonlinesolutions.comxxxxxxxxxxxxxxxsales@pcsonlinesolutions.comxxxxxxWebAssist.eCartPHP.Pro.ECOArts & Entertainment Articles PackagexxxxxxxxFailurexxxxxxSecurity errorSecurity header is not valid10002Error2.201311648