Here is the scenario we found.
1. You configured our module in test mode.
2. And Few Orders were placed on the store at that time.
3. Now you updated the configuration to live mode.
4. When you try to capture the order, it throw an error.
But you want to recover those test orders as live order, which is not possible.
“Recovering the Test order to Live is not possible from our end. In case if Paypal could do that kind of transaction recover, then please contact them and they will do that from your paypal manager account itself.
OR you need to contact the purchased customer and get the payment for those orders using an offline payment method.”
We hope this will help to solve the issue.
Paypal Modules: http://www.modulebazaar.com/en/modules/paypal-modules.html