Inteet is accessible through cable, but says no WAN detected when connecting the cable to the router

I connect my mac osx through a cable directly and it works fine. But if I plug the same cable on the router and connect the router through address 192.168.1.1, it says no WAN is connected. I've tried on Both of my routers which are all TP-LINK. On the router itself, the hint light is not on either. How could it be possible? Is there anyone who can give me some idea? Great thanks!

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