Communication failed between UR5 and OMRON PLC

Hi,
I am having issue where UR Cobot has sent command to Omron PLC but the PLC has failed to reply to UR Cobot.
At times, the PLC can reply to UR Cobot and run the program smoothly and after a few cycle times or after changing UR Program file around, the communication issue comes up.
I am using TCP/IP communication between UR COBOT and Omron PLC.
Is there a way to improve the communication?

Much appreciated with any help.