This should be due to some component between the router and the PC. e.g.:
- Network adapter in the router (does the socket flash green?)
- the network cable itself (try a different one, maybe it will work)
- the network adapter in the PC (does the socket flash green?)
- a switch, if available (is it flashing wildly?) Reboot and plug in one LAN cable after the other).
Or a setting in the router. But it should work with the factory setting.