I know my username and password. When I login using a correct username and password it momentarily logs in I see the dashboard and then it flashes back to the sign-on/login page. It does NOT tell me “Invalid username or password” so I know the credentials are correct. I can log in via my mobile device with the same username and password and it works.
I have the same problem and have tried IE, Firefox and Chrome; always with the same result; the dashboard appears briefly and then returns to the login page. I saw on another thread that a reboot of the machine can correct this but it doesn’t inspire confidence; I have only had the device for a couple of days!