Why does it say my recovery key is incorrect every single time that I try to turn it on?

I’m trying to set up a recovery key for my Apple ID. It gives me a key, I write down. I triple check that it’s correct and hit next. I verify the key, and it tells me it’s incorrect. So I try again. Still incorrect. I go back, get a different key and try again. Still incorrect. I am making 100 percent sure that I’m typing the right key but no matter what I do, it tells me it’s incorrect. What do I do? I would really like to have a recovery key for my account.