Requesting assistance with Feitian K40 Security key for MFA.

Hi flook007,

Thanks for posting in Apple Support Communities.

We understand you're having trouble with your security key used with your Apple ID. Could you provide details on the issue?

Use a security key to reset your Apple ID password

If you forget your Apple ID password, you can use a security key that’s paired with your account to reset it.

1. Go to Settings  > [your name] > Password & Security. (If you aren’t already signed into your Apple ID account on your iPhone, first use your paired security key to sign in).

2. Tap Change Password, then follow the onscreen instructions.

Use a security key to unlock your Apple ID

If you try unsuccessfully six times in a row to sign in to your Apple ID account, or if your iPhone detects other signs of suspicious activity, you’ll receive an onscreen notification that your Apple ID is locked.

You can use your security key to unlock it.

1. Tap Unlock Account, then follow the onscreen instructions to unlock your Apple ID.

2. If you think your account might have been locked because someone else knows your password, tap Change Password and enter a new one.

3. Tap Done.

Remove security keys

You can pair up to six security keys with your Apple ID. If you reach the limit and need to pair additional keys, you can remove one or more of your paired keys. You can replace keys you’ve removed at any time.

1. Go to Settings  > [your name] > Password & Security.

2. Tap Security Keys.

3. To remove all keys, tap Remove All Keys, then tap Remove.

4. To remove individual keys, tap the ones you want to remove, then tap Remove Key.

Note: If you remove all security keys from a device, the device reverts to using six-digit verification codes for two-factor authentication.

You can find these details in Use security keys to sign in to your Apple ID account on iPhone - Apple Support.

Regards.