Can't Send Code to Phone, Desperately Trying to Get Old Account Back

If you know your account details and can't use the other options then try going to https://support.xbox.com and click on Contact Us. If it requires sign in then create a new account with a different email address. Ask to be escalated to a Microsoft Advocate and see if they can adjust your contact info from there.

Quick update. I discovered the email tied to the account thanks to Microsoft Support. However, it's an AOL account I haven't used in many years, and AOL permanently deletes unused accounts after a certain amount of time. I contacted AOL to reinstate the account, to which they said there's just no way they can do it. Wonderful. Still have the cell phone number linked to the account, but apparently, I cannot use it to recover my account, per Microsoft Support. So now I'm trying to sift through generic AOL support responses given by their agents to reactivate the account, as the Microsoft Agent assured me the AOL account is absolutely still available since if it was permanently disabled, my Xbox account would have gone with it.

OK, thank you for the tip. Might take a week or so, depending on their response rate, but I will update the forum once the issue is resolved.

How do I set this up if I can't even access the account to configure the proper settings?

Sorry to hear it. If you're having trouble with getting a code to your phone I'd like to suggest downloading the Authy app to your desktop and see if you can add Microsoft to it. It will supply a useable code for you.