it depends on who is validating your logon. if you are gettng validated through a microsoft account you can contact microsoft.
https://support.microsoft.com/en-us/help/12429/microsoft-account-sign-in-cant
if you are attempting to log in to a local account you and you know you are using the correct username and password.
make sure you are not actually trying to login to a online account when you mean to use a local account name.
there are some issues that will mess up logons. Cap locks key, keyboards that have a stuck control key, bugs in keyboard drivers. you might unplug your keyboard and plug it back in, hit the backspace key a few times before you type in your username and password.
if you have any other active accounts on...