Fix for OpenCart Error: The security header is not valid

Posted Feb 23, 2015
Last Updated Feb 24, 2015

I've been working with OpenCart for the past couple days and ran into a problem that had many posts on the Internet with no solutions in my searches. So if you a problem with the PayPal Express Checkout in OpenCart, you may find a solution below.

The error on checkout was always this: "The security header is not valid"

What I did to solve this in the OpenCart Administration:

  1. In System > Users > APIs: Deleted the API user.*
  2. In Extensions > Payments, Uninstalled Paypal Express Checkout.
  3. Reinstalled Express Checkout.
  4. Re-entered the Paypal API info.

* Although in my case, I started with deleting the API user, I don't think it was actually necessary. I'd skip step 1 as a test if you have that problem.


No HTML Tags are permitted.

Comment awaiting approval.


Jan 6, 2017

Found the same issue, i had copied and pasted from Paypal site with credentials, it had copied in some leading spaces in one of the fields. took those out all worked fine so maybe worth checking the enties are correct in their fields. This article helped me go back and find the issue, so thanks for that.


Sep 5, 2015

Gracias. Fue la soluciĆ³n!!!!

Shawn Olson

Sep 5, 2015

You are welcome.
Angry Teapot Level Design Awards

Newsletter Subscription