Paypal gateway error: Please check your submitted credentials: security header is not valid

Summary

You may experience this error when you try to set up the PayPal Express checkout gateway with API credentials directly from your PayPal account.

Following are the two major reasons for the error:

1. Using incorrect API credentials while configuring PayPal Express Checkout
2. Configuring Chargebee's test site with PayPal's live site credentials or vice versa

The above error indicates you are using incorrect API credentials. If you are convinced that credentials are correct check the endpoint. You can also contact Paypal support for more information on your Paypal API credentials.

Kindly contact support if the issue persists. Here's our document on Paypal Express Checkout for your reference.