login xbox360

It will not let me login using my email and password on my xbox360

I can't login to my microsoft account from neither my xbox360 nor online via the website.

Where is "Remove all security info" located? Is this on Microsoft.com? Xboxlive?

I powered cycled the console but without a improvement.

Whatever device I use (WP8, Windows 8, Xbox360, Xbox One) I need to agree the terms and conditions every time after login.

Ok, here is the story with real names. Last Tuesday my son was using his xbox360 at school with a gamertag of buddyboycoco associated with his Microsoft account. Friday he came home and on another xbox360 he created a profile which gave him a default gamertag
of . When it asked for a login he entered the same Microsoft account login as buddyboycoco. That changed his gamertag for his account from buddyboycoco to . How do we get buddyboycoco back for this account? If we try and change
it back to buddyboycoco it says "buddyboycoco is taken. Please try another."

Thanks for your help.

visit https://account.live.com and sign in, select "security and Password", you most likely will recieve a 2nd Login Screen. there is an Option "2step verification", either deactivate it or Setup an
app Password to use on your xbox360.