Security Header Invalid

Using cs-cart pro- linked to PayPal pro. Using connection as “signature”. I keep getting the error “security header invalid”. The card info never gets to PayPal.

I have checked with cs people who say its because I used the signature for test purposes. So I changed the signature and I still get the error message. Any idea what is going on?. I just went live and cant get the first order thru.

I am also using Webgraphiq module and the express Paypal. What I get is an Security header is not valid error message…

You cannot use a live PayPal API signature in test mode, you need to use sand box API for that. In live mode is working like a charm.

If I put it in live mode paypal reports this error

[color=#333333][font=Arial, Helvetica, sans-serif][size=3]This transaction cannot be completed…[/size][/font][/color]