active merchant paypal gateway security header is not valid issue

Question

I followed this railscast to set up active merchant on a rails 4.1 app.

While I try to create orders and pay, I get the error from paypal server:

Security header is not valid

My question: What is wrong in my set up to have that kind of error ?

By the way does anyone knows what I can fill in cvv field for fake credit cards created with sandbox accounts.

Answer 1

Security header is not valid error comes in when :

1. You are in the live mode but you have used the credentials(API username, password and signature) from the test account or vice versa. Make sure if you are in test mode you take the credentials from sandbox account.

2. If the credentials are indeed incorrect. Make sure you haven't pasted any space while copying and pasting the credentials.

These are the two possibilities for this error.

Regarding the sandbox credit cards, yes you can use any fake credit cards using any fake card generator.