Check list

Is the device (PLC) that you are trying to communicate with connected to the power supply?
Wrong network parameters in the CP or PC.
Is the cable between PLC and PC/IPC connected correctly? (check LEDs)
Are the used datablocks defined correctly in the PLC?
Fetch event activated although you want to read more than just data blocks.
Have you analyzed the error text file (which errors did occur)?
Send the zenon to support@copadata.com