Cannot sign into Xbox live on the 360 [Error 801540A9]

So recently I bought an Xbox 360 during this pandemic, and I am unable to sign in. I should probably preface this with the fact that I have made the account on not a 360, and am signing in there for the first time (if that is important).

Anyways, I keep getting the error 801540A9.

I never had 2FA on (I tried turning it on and using the app password, then turning it off again to no avail). This account also does not have a parent/child account thing going on. I also tried waiting a few days and seeing if that might fix the issue; it did not. Basically, anything that I found online did not help unfortunately.

I am able to connect to Xbox live as I was able to log on with another account I had, but I would like to use this one (aka the one I'm on right now) as it has progress/other stuff that I want.

Help would be greatly appreciated. Thanks.

:)