A Microsoft file hosting and synchronization service.
Hi Niv,
I Hope you have the consent of the person you are trying to unlock the account. What happened to the account which you cannot access?
Do you see any option like one that says you can sign in with another method, such as a code sent to your phone or an authenticator app?
Run the sign in helper tool:
https://support.microsoft.com/en-us/accounts-billing/manage/microsoft-account-sign-in-helper
If nothing works, file the recovery form:
https://support.microsoft.com/en-us/accounts-billing/manage/help-with-the-microsoft-account-recovery-form
I look forward to hearing from you to get the results of the troubleshooting.