Q: I just installed a new ecobee and I'm getting a communication to interface failure. I have a 4-wire cable going from the stat to the equipment interface. I double checked to make sure that it was wired correctly: 12V, Gnd, Data+, Data-. The 4-wire cable is 20 gauge and the cable is about 15 feet long. I put an ohm meter on the cable and verified there were no breaks in the cable. I also made sure the terminal block was not clamped down on the insulation.
A: If the red "communication" LED is not on then the messages you are receiving are just cached error messages. Continue to hit "ok", it may take quite a few times to clear the messages but this should fix it.