Hello, Aswin
It is quite unexpected that such a problem is still not resolved after more than 1 month and a lot of efforts from the best members of this community.
It seems like we are missing some critical piece of the information. So, could you please answer EACH of the following questions in AS MUCH DETAIL as possible?
(please do not give us just a simple one-line reply…)
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We are assuming that you are using 2 (two) good quality normal Ethernet cables (Cat5E or better, with RJ45 connectors on both ends) connected between your notebook (PC), unmanaged L2 switch and the ETH port of the C80 device (PLC).
Is our understanding correct? -
Are there are any other network devices connected to the same L2 switch?
(if so, please disconnect ALL of them, at least temporarily) -
Assuming that “Port 1” of the switch is connected to the notebook (PC). Do you see 2 LEDs active?
(one should is steady ON, indicating a “link” and another one is blinking at some rate indicating a data transfer) -
Assuming that “Port 2” of the switch is connected to the ETH port of the C80 (PLC). Do you see 2 LEDs active? (as described above)
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If the answers to both questions #4 and 5 are YES, please provide us with information about the IP address and netmask of both notebook (PC) and the C80 device (PLC).
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Can you ping the C80 device’s IP from your notebook?
(use “ping -t” command to send an unlimited number of pings; interrupt withCtrl-C) -
What is the success rate of the pings ?
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Launch Automation Studio, open the project which has been loaded into the C80 device and send us a full screenshot with at least the following details:
a) Online Browse" view of a Ethernet network
b) bottom status bar which shows the device model name and its status (RUN, SERV, etc)
Well, I hope after getting your detailed answers to all of these questions we can come up with some suggestions and hopefully solve the problem! 
Thanks and Best Regards,
Alexander