Could you post a screenshot of the connection settings of the new TP-Link Archer vr400 and shoot us a PM with your details to better understand the situation.
When I moved house my Asus DSL-55U modem that I have been using for a couple of years would not connect. The NBN tech said that the modem must be faulty so I plugged in my ancient Huwawi modem and that connected.
I bought a new modem (Tp link Archer vr400), I followed the setup instructions for this modem on the Tpg site but the modem is saying that the dsl cable is not connected.
I have also tried changing the telephone cable.