Hello.
Could you post the contents of your /var/log/xx_Generic_Serial_Device.log, where xx is your device #.
The most common reason that this error occurs is that your device data is incorrect.
For ethernet devices, you need to make sure that the TCP Port device data is defined, and that the correct port is specified. You also need to make sure the device has an IP Address specified, so that it knows where to connect to the device.
-Thom