Why isn't my 10+ year old gamertag linked to my Microsoft account

I've only ever had the one account I used an old email to start my account originally, but I have since updated it and used my updated info to sign in on two previous consoles. But since signing in on my new console, I can't find any mention or history of my gamertag on my Xbox account anywhere

Hi, I hope you're doing great out there. I am an Independent advisor and I am here to help you in regard to your concern.

This may mean that you’re signed in under the wrong Microsoft account. Kindly check all Microsoft accounts that you own via https://account.xbox.com/profile and check if you will see your Gamertag, friends, achievements, etc.

Which gamertag is linked to your Microsoft account? The new one or the old one? My guess would be that your old account is still linked to your Microsoft account and you are trying to use the new gamertag but the old one is interfering. Check this link out
on transferring gamertags
support.xbox.com/.../switch-gamertag-to-different-microsoft-account. If that isn't the issue come back and let us know if we can help further troubleshooting the issue.

I'm trying to re-associate my old Microsoft account (with a Google address) with my current gamertag. I did learn that the old account was indeed associated with a free Silver gamertag for reasons I cannot remember. In order to make the switch to the old
account, I renamed the old account with a new email address, in hopes that I could somehow reclaim the old address. However when I tried to rename, I received the error: 'email isn't available'. What happened to it? Why can't I reclaim it???

I just changed my gamertag and the EA account says I still have it linked to my old gamertag. I haven't changed my Microsoft account at all only my gamertag. I can't get it back since to change your gamertag it has to be under 12 characters and my old gamertag is 14 characters.