I think they think you are not the real owner of your account because you no longer access with your 2FA authenticator.
If you have the secret code, you can recover your 2FA to another software like Google Authenticator; it does not ask for fees and it's free and once you recover your 2FA regenerate a new secret code from Kraken, and make sure you write down your secret key offline.
If you didn't save your secret, then your last option, as suggested above, is to contact support.
Try contacting them on X here
https://x.com/krakenfx
I most likely did keep the recovery key but I have no idea where (I know that is bad! and I will start a search now)
Why not try use the search in your file explorer. If you want a faster search tool you can try to download "everything" then search the file. You can try few keywords like" secret key"," "backup," or "authenticator."