CD58, if you are still struggling to find your router, download an app called Fing onto your computer. Scan for viruses before you install and open it. It will show you all devices on your network, by name.
Thinking about it, Your Tp-link is also a router, and in fact is your primary router. Your Asus is your secondary router, and will take its IP address from the primary router. So it will be the same as the primary router address, except for the last digit (or pair of digits).
Remember that any device connecting directly to the TP-link, will not go through the VPN, as you would be by-passing the VPN router.