title: PayPal gateway has rejected request. Security header is not valid (#10002: Security error Magento
body: <p>up the pay-pal advance in magento . I have fill all the credentials in magento admin . BUt when i go to frontend and click pay-pal button it gives </p>
  
  <blockquote>
    <p>PayPal gateway has rejected request. Security header is not valid
    (#10002: Security error</p>
  </blockquote>
  
  <p>i have googled a lot and found some suggestions like </p>
  
  <blockquote>
    <p>Remove API Username, API Password and API Signature from
    Admin->configuration->Paypal->API/Integration Settings. clear cache
    and test again</p>
  </blockquote>
  
  <p>i have tried all these but it still gives the same error.</p>
  
  <p>Please suggest me what can be the issue</p>