Met with Robert and proceeded to diagnose the issues with the thermostats communicating with the out side temperature sensors. I pulled off the outside sensors to check the batteries. Noticed batteries not fully seated. Robert provided replacement batteries. Inside thermostats were giving a communication error code. Pulled the thermostats off the wall and documented the type of battery needed. I drove to the local hardware store and purchased two new lithium cell batteries for the thermostats. Replaced the batteries to the thermostats, reset the date and time. All error codes were cleared. Units are operating and behaving as they should. No more issues. Robert was very happy with the service.