@n5wuser,

Do you still have a modem in between your ISP and your Deco Router? A modem is still required for a connection, it is just that your previous hardware was most likely operating as BOTH a router and modem. This is either rented from your ISP, or you will need to purchase one outright. If you have the previous hardware, you can look to see if you can enable passthrough or bridge mode on the device, which would essentially make the device operate as only a modem.

If you do have a modem, you can change the DNS server settings from the app on your phone to a different DNS server such as Google's or Cloudflare to see if it is more successful. Otherwise, I would recommend removing the Deco from the network and attaching your PC directly into the modem and seeing if the issue persists. It is definitely strange that you are able to successfully ping servers, but it cannot resolve the name.

  @n5wuser,

That makes more sense now. The Deco X50 wasn't actually released in the US, so I was curious as to why you had one.

I would recommend taking a look at the resources provided by the AU website as there is additional info that we don't normally know about. For example, NBN Compatible Device Checker. Your Deco is there btw.

I also found this walkthrough which mentions that there are a few settings that you should ensure are disabled when setting up an NBN connection with Deco.

How to set up TP-Link Deco for NBN FTTC

Otherwise, I would recommend posting to the Global EN forums to see if any other international users can help you get connected.