Sending, receiving, and organizing email in Outlook.com
Hello,
Just to clarify, are you being asked to enter your Microsoft account password, a Windows Hello PIN, or a security verification code?
If you tried to sign in with your Outlook email address and password and Microsoft asks you to Verify Your Identity through your old Phone number, but you no longer have access to it, you'll need to replace the Security information.
That is, on the Verify Your Identity screen, select 'I don't have any of these' and follow the prompts to replace it.
If you are on the same screen shown in the screenshot and don't have access to your phone number, it is recommended to replace the security information.
Note:
If you remove all of your previous security information and replace it with something new, your account will be put into a restricted state for 30 days.