Try a reset of the NBN HFC NCD (Network Connection Device - Black Box Arris).
On the back of the NCD-Black box there is an reset button (needs a pin clip to press) Press this and count to five, all LEDS should go out and then reset to green.
Once Modem gets WAN connection, then retry web browsing.
Watch our short video guide on how to set up your NBN HFC service. Visit https://link.tpg.com.au/tsaoQD "