The E294 error means your thermostat needs an R wire but there's a configuration issue. You'll need to reset your thermostat to factory defaults and add it back to the Home app. Be sure to enter the correct wiring info when re-adding it to the Home app. I'll put the detailed steps below. Hope it helps!
Next, add your thermostat back to the Home app. Tap Add + at the top left of the home screen and follow the instructions on screen. Pay extra attention to the instructions when you re-enter your wiring info. If it's still not working, check that your system wires are connected to the right connectors. Use the wiring diagram the app gave you during setup to move the wires to the right connectors.
If you don't have the wiring diagram, refer to the picture of your thermostat wires that you took when it was installed. If you didn't take a picture or can't find it, follow these instructions to access your system's control board and take a picture of the wires. Use this picture to enter the wires into the app.