PayPal gateway has rejected request. The transaction id is not valid (#10004: Transaction refused because of an invalid argument. See additional error messages for details).
This error has popped up all of a sudden. It used to work perfectly fine. This error occurs while trying to invoice an order in Magento backend.
There was an issue with PayPal this morning. It should all be working again now (our store is) https://www.x.com/content/resolved-major-impact-express-checkout-paypal-apis-virtual-terminal-and-website-payments-pro
That could be due to wrong currency.
Please check this: https://cms.paypal.com/uk/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_errorcodes
