Existing master socket and extension socket

[luckysh0t]

My bt infinity currently has a master socket connected to one of 2 internal cat5 cables that terminate in a twin box that has another two similar cat5 cables (together with an external black cable for each as well) which presumably was for use in the days of two phone lines for faster dialup.

In another room there is a 3rd socket wired which I have been trying to use as my router's connection point to no success. I connected the spare cat5 blue/orange in the original connection box to the VDSL AB extension connections then tried connecting the same pair to 3 & 4 of an rj11 euro module on both sets of cat5 on the 3rd extension socket, but neither gave me a broadband connection when I hooked up the bt smart hub 2 to it.

I guess there's a million reasons why a 20 year old wiring extension isn't working anymore, but assuming it wasn't something wrong in the cabling, is what I've done the correct procedure to use the 3rd socket as my connection point for the router?

I guess I'm just presuming the 3rd socket is an extension for the current active cabling?

[Someone-Else]

You need to check the cable with a multi meter first.
It may be the wrong cable