PayPal Error: Security header is not valid (Code 10002)

This error, seen when attempting to checkout using LifterLMS PayPal, is generally the result of having miscopied credentials from PayPal into the LifterLMS PayPal Checkout Settings screen or using LIVE credentials in Sandbox mode or vice versa.

This error can be easily resolved by updating your credentials and ensuring they are correct.

However, if your credentials are correct and you’re still having issues, PayPal document the error as having the following causes:

Account locked – The user account is locked

Authentication/Authorization Failed – Account is locked or inactive

Internal Error – Account is locked or inactive

Internal Error – Internal Error

Authentication/Authorization Failed – Account is not verified

Authentication/Authorization Failed – API access is disabled for this account

Authentication/Authorization Failed – Client certificate is disabled

Authentication/Authorization Failed – Internal Error

Authentication/Authorization Failed – This call is not defined in the database!

Authentication/Authorization Failed – Token is not valid

Receiving Limit exceeded – You’ve exceeded the receiving limit. This transaction can’t be completed

Restricted account – Account is restricted

Source: https://www.paypal.com/va/smarthelp/article/why-did-i-get-api-error-code-10002-ts1030

If you’ve confirmed that your credentials are correct and you’re still having issues please contact PayPal for further assistance.