If you have done all settings correctly, and you are using the correct cable with the correct pinout, but the connection still having a problem, then please check your network settings and make sure that you have an IP, a Subnet and a Gateway set accordingly. We also recommend to use the first en0 network connection and to assign a fixed IP address and not to use a DHCP address.
Warning: The Moxa box is currently not supported when using OSX 10.13 or higher.