If you are having problems communicating with a Morningstar product using a serial connection, try the following:
Make sure that the unit is powered with a battery or power supply. The unit cannot communicate without power.
Verify that the serial cable is not a Null Modem or cross-over cable.
Verify that no other programs or managers are using the same serial port.
Check the serial cable for continuity using a multimeter. The cable should have continuity from Pin1<->Pin1, Pin2<->Pin2,… If possible, try another cable.
Shut down and restart the PC. Reattempt connection.
Try another PC
For products that require the PC MeterBus Serial Adapter (Model: MSC), check the RJ-11 telephone cable. If possible, try another cable. It has been reported that some USB to Serial cables will not work with the MSC because the RS-232 output signal voltages are below the RS-232 electrical specification.