Some of the common problems with implementing UCM/Modbus will be shown here
For UCM/Modbus-ETH03 configured as Master, connecting to a Modbus Slave device, the IP address of the UCM/Modbus may need to be specifically allowed to connect to the Slave. There may be a setting on the Slave device to allow certain IP addresses, or all IP addresses to connect. If the UCM/Modbus is not able to connect, then in Comfort Server Manager, the IP address of the UCM/Modbus will be Idle, instead of Busy when it is connected.