Wow. This likely implies you got vouchers dated December 2021. I guess refundable since bought in August 2021 and then the "refundable without questions asked" scheme was still in place. Formally, they expired in December 2022. Since bought via AF, indeed AF should help. I assume you do/did not have an FB account, otherwise you could have asked to convert the voucher into a refund via the FB site, but apparently you did manage to do something like this via the AF site. Do you have proof (e.g. screenshots) that you asked for this and they were processing it? The more hard proof you can show you were asking to convert the voucher into cash well in time before the 1 year limit, and the more you can prove AF was not taking action, the stronger your case. With all this I simply would go back to customer care but also file a complaint. Do everything in a way that is traceable. Phone calls are not.

It is incomparable in terms of stakes, but you are not alone banging your head to the wall with AF/KL refunds or compensations. For me in June 2022 3 flights on 3 different journeys were cancelled leading to 3 overnight stays which I had to pre-fund. Filing this with KL/AF is a nightmare - they asked for one case more information via e-mail (more detailed bills, say 150 Euro), I filed that around 4-5 times, up to two times for this case I got an automated email 'since you did not react, we are going to close your case number'. The problem there is the system gives 2 weeks to react, but the e-mailed answers have to be processed apparently manually and they do not manage to do this. It could be work overload, but I would not exclude a deliberate strategy to deny all such claims as long as possible in the hope that many give up.

Good luck & courage. It seems that is unfortunately needed when dealing with AF/KL customer care these days.