Thanks @BarryCarlyon for your reactivity.
Changed the redirect Url at both sides (twitch and App) like you suggested
http://www.my-domain.com/user/sign-in/oauth/?authclient=twitch
No luck. Got redirected to
http://www.my-domain.com/user/sign-in/oauth/?authclient=twitch&error=redirect_mismatch&error_description=Parameter+redirect_uri+does+not+match+registered+URI