Upgrade from Linux 3.10-ltsi to Linux 4.14.73-ltsi

I have recently upgraded my PC custom board from a Cyclone V SoCFPGA from Linux 3.10-ltsi to Linux 4.14.73-ltsi. Trouble is, I cannot connect it to the internet anymore, with error code being “failed to bring up eth0” when dhcp tries to assign an IP to the unit. Can someone point out how can I get it to work online?

You have to manually assign IP address to eth0 and configure it
or restart your Network service.
what is your current OS that you are using?