I am unable to sign into account on xbox 360 games, playing from xbox series x

I am trying to play Black Ops 1, and I am unable to sign into my xbox account when it changes menu to xbox360. I cannot download my profile because when I put in my information that I know is correct, it does not work. I changed my password too and still it will not work. I am trying to play zombies with friends but I cannot sign into my account. My internet works and there is no problem on that side, I just cannot connect my account. Any help would be appreciated.

:)