First, check to make sure that your scheduled setpoints are within the the min/max cooling and heating setpoints on the configuration page. If this is correct then check your inactive schedules to make sure they are within the min/max cooling and heating parameters. Even if the schedules are inactive, it could cause an issue if the parameters are outside the min/max setpoints.
From the PC software, Cloud Connect, or directly from the IP address of the thermostat in a browser go to the schedules tab. Check the active box above the schedule number then set the time you would like the schedule to start. Enter the setpoints you would like the schedule to reflect, the cool temperature will be the maximum temperature that will be reached before the air conditioner will turn on and the heat temperature will be the lowest temperature that will be reached before the heat will turn on.
With the faceplate connected to the backplate, look through the top vents of the backplate. If you see a red LED illuminated on the backplate then the backplate and faceplate are not communicating. If you do not see a red LED on then the backplate and faceplate are communicating.
Look at the backplate with the faceplate off. There are two LEDs on the PCB, a green LED and a red LED. If the green LED is off then the thermostat is not communicating to the WiFi network. If the green LED is blinking then the thermostat is in ad hoc mode and is ready to be put on your local network. If the green LED is solid then the thermostat is on the network and communicating.
Make sure that you have setup an account and that it is not expired. Make sure you are entering the correct email and password. If you cannot remember your password hit the "forgot password" button at the login page. If you have confirmed that the login credentials are correct, contact support and let them know you are having an issue.
Check to make sure you are on the same network. If the green LED on the backplate of the thermostat is solid then it is connected to a network, your router settings may be preventing the Device Explorer from detecting the thermostat.
Make sure the thermostat is out of the ad-hoc network state (netx-setup) and on the network you are connected to.