Please check your RS232 wire is connected directly, the cable length is recommended less than 25m. Make sure cable is working and functioning correctly. If doesn’t, should change the cable.
Some serial adapters can cause communication problems. Try using another computer or laptop for testing. If you have access to a serial port loopback tester / analyzer, use that to confirm that there is no problem with the port / cable.
Finishing the cable. Most cables are adequate up to 15 meters. If you have a long cable, do NOT coil it, as it can increase capacitance, and then corrupt data. If it passes close to many electrical cables, or inductor motors, such as washing machines and refrigerators, they can also cause interference. We suggest you limit the cable to 15 meters.
If you are using a RS232-to-USB converter, make sure the driver had been installed properly. Check the serial port status and COM number in Device Management->Port (COM and LPT). In addition, watch screen of the inverter to make sure inverter’s COM address had been set to “COM Address: xx” (Fixed address, example, COM Address: 01)