Error: Security Header is Not Valid 10002 (PayPal)
Error Message: 10002 Security header is not valid.
Cause: This error indicates an issue with the login information you are using for your PayPal connection. It is usually seen with PayPal Website Payments Standard or Pro.
Resolution: Remove your credentials, then re-enter them. If you copied and pasted the data, make sure there are no spaces before or after the information. We recommend first pasting them into a text editing program such as Notepad or TextEdit to ensure this.
If this doesn't work, contact PayPal Support to have new credentials generated, then enter those new credentials (again pasting into a text editor to avoid extra spaces).
One more thing... Make sure that you are not in test mode on either this page or within your PayPal account.