The PayPal transaction will continue to show as pending in your account until we are able to obtain the authorisation to charge your funding source. PayPal do not advise us as to the reason for the failure, but the most common reason is that the card issuer/bank has refused the charge. We can re-attempt to charge your funding source again, and please contact us if you wish us to re-attempt the charge.
If you would rather replace your order using your card details you would need to place a new order and give your card details in at the checkout stage and contact us to cancel your PayPal order.
Learn more here.