Can't Access my website (Joomla) but I have cPanel login

I believe this is an easy technical issue rather than security. or something I don't understand with Joomla 3 protocols. I was editing my Joomla template (Joomlart) and suddenly I couldn't access my administrator page, first, there was third field asks for (Secret Key), Now there is a message says: "Username and password do not match or you do not have an account yet." I created another admin users thru DataBase (cPanel) but they all denied.