recovery key

See -> Two-step verification for Apple ID

Two-step verification for Apple ID

👉 scroll to & read -> What if I lose my Recovery Key?

You can sign in to your Apple ID account page and create a new Recovery Key using your Apple ID password and one of your trusted devices.

1. Go to appleid.apple.com/uk.
2. Sign in with your password and trusted device.
3. In the Sign-In and Security section, click Recovery Key > Change Recovery Key.

Keep your new Recovery Key in a safe place. Your old Recovery Key won't work any more and you can't use it to reset your password or access your account. If you can't see Recovery Key in the Sign-In and Security section, then you are not using two-step verification. 

👉 FYI: Write down your recovery key and keep it in a safe place.

Looks like there's a bug when trying to use that recovery key.

Please try again later.

Or get more help:

• Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support

• Contact Apple Support -> Get Support (apple.com)

So create a new Recovery Key using your Apple ID password and one of your trusted devices, see link in my previous post.