How do I sign in xbox 360 live when my account is already there

I'm having the same problem. I can get online. My avatar shows I'm signed in but when I go to the store (Minecraft) it says I need to create an Xbox Live account. When I go to Xbox Live signup it says I'm already signed in. When I try to create an account
using my Windows and Xbox Live account info it says the credentials are already being used (by me).

Part of the problem I'm having is when I'm signed in with the Avatar, I don't know if that's the windows live account or the Xbox live account or something else. I doesn't say, which is not helpful. I can log into both windows and xbox live on my computer.

How do I associate my gamertag with my Xbox avatar? Or, if that's not the issue, how do I resolve this?

I have signed in on my brother-in-laws xbox 360 and we have had a falling out. how do I deactivate my live account on his 360 console?

When I select join the backwards compatibility it sends me to a section to sign up for xbox live when I already do a 3 month plan. I'm signed in and verified, but I don't see the xbox 360 games on my xbox one games for gold section. Am I missing something?
I don't see any ready to install xbox 360 games on my xbox one either even though I have dozens linked digitally to my account.

To play games, even on Xbox 360, it has been required that you're signed into an Xbox Live profile (aka Microsoft Account). It's possible that previously it was configured to automatically sign in, and you didn't realize. It's possible that the account
that had auto-signed in removed the device from their account or changed security settings, and would require reauthorization to sign in.

Now, that is speculation on what might have happened as to why you're seeing a sign in screen unexpectedly. But the point would be that previously when using the 360, there was an account/profile being used.

This page here has details on how to add a profile to your Xbox 360. That would be for if there isn't
one present. Do you see if there is a profile already on there?

+ when i try to connect on xbox live while already connected offline with my account," xbox tells me i need a xbox live account to continue " and propose me to either : SIGN UP / SIGN IN / NO THANKS.

SIGN UP : simply doesn't work... when i press A on it, nothing happens, it make a little noise and thats it, even if i'm connected to internet

SIGN IN : when i click it, it shows that i'm already signed in with my account, and the only option are to sign out or cancel. no of those are what i want.