Managing personal Outlook.com account settings, security, and privacy
Hi,
Adding a phone number is not working for other users as well, for which I have seen reports since yesterday. Please wait for a day or two, this should get sorted out.
If you haven't already, please go to https://account.microsoft.com and send feedback in the bottom right. This helps thje team investigate.
A friendly reminder that this is a user-to-user forum where users help other users. Experts or Advisors participating here cannot make changes to Microsoft services or access internal systems and can only provide technical guidance, irrespective of Microsoft's Policy decisions.
I hope this information helps. If you have any more questions, don't hesitate to reach out. Wishing you good luck!