Cancel Two-factor authentication for Apple ID

From the article below. If it has been on longer than 2 weeks, you can't turn it off.

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, however, you can unenroll for a period of two weeks. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require a higher level of security.

Apple ID -Two-factor authentication

1. Open any web browser on any computer and go to appleid.apple.com
2. Log in to the Apple ID you want to disable two factor authentication for, you may need to use two factor Authentication to gain access to the account
3. Go to the “Security” section of account settings and choose “Edit”
4. Locate the “Two-Factor Authentication” section where it says the feature is ON, and click the link to “Turn Off Two-Factor Authentication”