The recovery key generated is 7 blocks long but the Mac only accepts 6 blocks. There is no way around this. Please fix your system and stop giving silly answers like try using 6 blocks. It obviously doesn’t work. Fix your stuff…please!
This is not a helpful comment at all. They are asking for a recovery key. They should state it as such if it is prompting a 'file vault key'. It doesn't say that anywhere. If you want to be helpful, rather give a comment on how to find this so called file vault key, rather than telling me 'it's not a bug'.
The system is broken because they aren't using the correct language and prompting for such. Again please fix your stuff.
It’s not a bug. You are being asked for your Mac file vault key which is 24 characters. The 28 character key is your Apple ID recovery key.
Google gives the following advice on the first hit, it looks like it could help you: https://www.macworld.com/article/231249/how-to-find-your-filevault-recovery-key-in-macos.html
Recovery key generation
