Unfortunately, it is not possible in P2P to reload (Load option) the remittance files for Invoices that have already been paid. Your load will failed giving you an error saying something like: Remittance cannot be reloaded for an invoice that's already processed.
If you have the Remittance files that were already loaded for that invoice, you could probably try reloading the corrected files using the "Update only" option. Not sure what that would do. If you do not change mandatory information (such as reference Invoice ID...) it would probably update the existing record - but I cannot say that for sure, you'd have to try on your test realm first I guess.