10415 – Transaction refused because of an invalid argument.

Hi, I tried a test purchase after setting up my site this morning though after I confirmed payment on the paypal page I was redirected to store/shopping-cart/confirm-checkout/ with the following message:

There was a problem finalizing your purchase with PayPal. Please go back and try again.

10415 – Transaction refused because of an invalid argument. See additional error messages for details. – A successful transaction has already been completed for this token.

Also at the bottom of the page it says:

Whoops, looks like you skipped a step! Please go back and try again.

When I click the ‘go back and try again’ link, it takes me back to store/shopping-cart/checkout/

and if I click the continue ‘check out’, it takes me back to the paypal page where I have to enter my credit card number again, BUT i have already paid!

I have received a email from paypal saying that my account has been debited. Also when I try to track my order with the order id from the paypal email, I enter the id and click ‘look up’ though the page does nothing and just refreshes?

This site is for a customer and I really need to get it sorted.