Thank you for posting your question about using the Plugable USB serial adapter with your DAQ. In looking up the manual for the ADAM 4018M, I notice that it requires a RS-232/RS485 Converter between the COM port and the DAQ.
If you are using one of these, I would suggest taking a look at the COM port settings, especially baud rate. The factory default setting for the converter is 9600 baud. The manual for the DAQ is here:
If you are using the converter, and the port settings for the USB to serial converter match the settings for the RS-232/RS485 Converter, let me know, and we can troubleshoot more deeply.
I just wanted to check back to see if you still need help with this.