Paypal express checkout not working

[DrByte]

We are sorry for the inconvenience. The PayPal account authentication settings are not yet set up, or the API security information is incorrect. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002) 10002 Security error - Security header is not valid

This means, as it says, that you've entered invalid information for the API username/password/signature fields in your module settings, and/or you've selected "sandbox" when it should be "live" or vice-versa.

[vmolasi]

You're right on. I was using Sandbox setting with Production server username. So the cart is getting redirected to the Paypal-website and the basic flow seems to be working fine. But the ipncheck.php still fails fo SSL check. Is this because of the proxy serve requirement by go-daddy?

[DrByte]

GoDaddy does weird things, so, the answer is "maybe -- most-likely".