xbox live can't sign in. When I enter my details it says this is linked to another account

log in here:
https://account.live.com/SignInPreferences?mpsplit=1

it seems you already have an email set up for the account so you will have to add the new one and delete the old one.

No worries. Please follow the instructions at this link to learn how to add and remove a gamertag on the 360 https://support.xbox.com/my-account/manage-gamertag-and-profile/add-remove-profile-xbox-360

My son can sign in to his account fine. When he is playing Fifa 16 and he wants to access xbox live it says the parent needs to accept the new terms. When I put in my email and password it says it is wrong. When I try to sign in to my profile it says error
8015D003 but all details I am entering are correct.

Hey !

I tryed to get it on my microsoft account but there is no option for redeem code it's just join xbox live and when i clicked on that it says: we are sorry, the page you requested can't be found!

Is it possible that I did something wrong in begining when i get xbox like maybe something denayed or disallowed for xbox live, or purchases...or should i return to a store and swap the code for another?

Try using this link: https://redeem.microsoft.com/enter

That's a direct link to where you can redeem codes (for games, prepaid currency and also Xbox Live memberships).

Again, make certain you are signed into the right account when you do this.

Let us know how you get on.

Just the code 8015190E when I do the connection test to xbox live.

It's strange I sign in my profile and it signs in no problem but when I start a game a message pops up saying I need to sign into Xbox live, when I'm already signed in. So I sign in and another message says the console can't connect to xbox live with the code 8015809E