Connect the PC to the router via Ethernet cable to confirm its Etherenet connection is working. Then connect one of the AV600 units into the Ethernet port you have tested on the router, and another AV600 unit to your PC to check internet connection again.
If internet works on the router but not through the powerline adaters, remove it to a different power outlet to have a check. Or test them in the same room. Or even re-pair them: press the Pair Button on each unit for 15s to make them leave the network, then press Pair Button on each unit for 1s to re-pair them.