hmm..
1. Remove the DNS settings and set it to get the DNS from the DHCP itself.
run the below command and paste the output here
It tells what are the DNS which are being provided (if they are) by the DHCP machine.

If you arent getting any output then its an issue with the DHCP not working correctly.

But the simplest way to check if there is an issue is by flashing the firmware again. Something you may have installed earlier might have caused an issue. Flash both the Firmware and the eMMC image.