Hi,
Microsoft has updated its account security system, and for improved account protection, phone numbers can no longer be added as a new sign-in verification method. Instead, Microsoft now recommends using a recovery email address, the Microsoft Authenticator app, or a passkey/security key as your primary methods for account security and recovery.
To manage or add your security information, please sign in using the link below:
https://account.live.com/proofs/Manage
Once signed in, click “Add another way to sign in or verify” and choose your preferred recovery method. Using the Microsoft Authenticator app or a recovery email is highly recommended because they provide stronger security and can help you recover your account more easily if you ever lose access in the future.
You can find more information in Microsoft’s official support article here: