Security header is not valid error message in woo commerce

[chocdetective]

Whenever I attempt a payment refund I see the same error message: "Security header is not valid". 

It sounds like there is an error in the handshake / protocol but not enough information in the error message to identify what.

I am using https://woocommerce.com/products/woocommerce-paypal-payments/ version 2.6.0

[MTS_Jennifer · Accepted solution]

Hello @chocdetective 

Thank you for posting to the PayPal Merchant Community.

Here is a document that has more details on the error message Security Header is invalid:

https://www.paypal.com/us/cshelp/article/why-did-i-get-api-error-code-10002-ts1030

Usually when you get that error message it means your API credentials are incorrect. This can happen if there is a space before or after any of the credentials. It can also happen if you are pointed to sandbox and are using live API Credentials.

Here is how to locate your PayPal API Signature Credentials:

• Log into your PayPal Account at https://paypal.com
• Hover over your name
• Click on Account Settings
• Click Update next to API Credentials
• Scroll down and click on NVP/SOAP API Integration (Classic)
• Copy the API User Name, Password, and Signature one at a time and paste into WooCommerce
• Ensure that there are no spaces before or after any of the credentials. This may require that you paste them into a text program and remove any spaces before or after the credentials.
• Ensure that you are pointed to live and not Test/Sandbox
• Save changes in WooCommerce

Thank you,

Jennifer

MTS

PayPal