Check list

Is the COM port in use by another application or are the settings incorrect?
Is the device (PLC) that you are trying to communicate with connected to the power supply?
Are you using a full-featured null modem cable?
Have you checked the LEDs at the adapter and interpreted them according to the adapter documentation?
Are the configured Net addresses available at the MPI bus? Did you specify them in the configuration?
Are the used datablocks defined correctly in the PLC?
Have you analyzed the error file (which errors did occur)?

In case of communication problems, the driver writes a detailed problem analysis into the driver communication error file. This file is stored in the project directory (RT\\FILES\\zenOn\\custom\\log). The name of the file is _<drivername>.TXT

You can view this file with any text editor, e.g. Notepad.

For additional error analyses please send a project backup and the "error file" to the support.