Paypal error #10602 on magento

Question

I am getting below error when making an invoice on a product

PayPal gateway has rejected request. Authorization has already been completed (#10602: Authorization completed).

I've read what's the error about ( here ) but I don't know how to fix it.

The product's status is still "processing" and I want that to be changed to "complete".

Short back-story: we migrated the magento site on a testing server first with a different domain name.

Answer 1

From that error, it sounds like you are trying to authorize a payment that's already been authorized. Are you trying to do authorizations? Try changing the transaction processing mode to sale.