Who is this article for?
This information applies to any Webninja customers who are using Paypal as their payment method.
the customer attempts to checkout using Paypal as the payment method and is redirected to Paypal's site to make the payment.
When they attempt to make the payment, they're confronted with an error stating:
This invoice has already been paid
and they cannot proceed further - resulting in a lost sale!
in your Paypal Merchant settings - you can make this update:
(NOTE: this is not for the end-user customer to do in their Paypal - the merchant who's receiving the payment needs to make this change in their Paypal settings)
go to: Profile -> Payment Receiving Preferences ->
Under "Block accidental payments": select “No, allow multiple payments per invoice ID”
This will prevent the error from popping up again for any further customers.