HI
It could be different problems, but so far, I can see 2 issue :
What is your configuration? Point to point or point to multipoint? Could it be possible that the router support only on of these 2 possibles configuration?
It could be also a problem of pair on your cable; the same pair should be use for one purpose (TX or Rx) but if you mix the wires, then you could have sever problems.