Hello, dear.
This alarm is generated because there is no communication connection between TCUC and SMU. You need to check if the RS485 connection between TCUC and SMU is loose or disconnected. It is also possible that the SMU version is too low to cause no communication with TCUC. It is also possible that the protocol between TCUC and monitoring is not unified. Single board J18 (1 2 pins) is not shorted for MODBUS protocol, shorted for master-slave protocol.