Alliance Broadband WAN Port not detected

I am having one of the most weird problems with my new Alliance broadband. I took the connection a few days back and it works perfectly with my PC. However, when I try to connect the ethernet cable to my TP-Link Router then the internet light never flashes. Upon entering tp-link manual configuration it says that "WAN Port not detected". I did reset the router and checked all the wiring but no help.
Thinking that the router is faulty I took it to my neighbour's house using same Alliance broadband and much to my surprise the router works perfectly without any hassle. What could be the problem internet seems to work fine when I connect the cable to my PC ethernet port. This is driving me crazy. Can someone please help me.
It might happen due to two reason. 1. Please check the WAN port speed and change it to 10Mbps in your TP Link router. I assume you have entered IP Address/netmask/Gateway & DNS properly.2. If Alliance Broadband doing MAC binding then you need to copy your PC's MAC Address to router.