I did have a couple of these cancelled flights back then (2020/2021).
AF would issue a refundable voucher valid one year. Those vouchers appeared on the website, and could be used for other tickets or you could ask for their refund.

As mentioned by atflyer, it could be that your vouchers expired after a year and you lost the money.

The "invoice" is another story and probably some of the usual AF IT response/bug when you might have recently inquired about the status of the refund.

A bit surprised that you did not pursue the refund more actively since August 2022. That is probably too late now.