EX6200 extender setup after NBN

I have followed your instructions to reset the extender, and then followed the Netgear instructions to setup with the Netgear genie. The setup went through as per the instructions with no problem and the extender networks mynetwork_2GEXT and mynetwork_5GEXT were set up. On the extender, the 2.4 GHZ indicator shows steady green, the device to Extender LCD also shows steady green. But when I select mynetwork_2GEXT or mynetwork_5GEXT, I still get No Internet Connection. The message on my iPhone says "if this is your Wi-Fi network, try restarting the modem and the router or contact your ISP". Is it an issue between Optus/NBN network and the extender? Should I contact Optus to get this problem resolved? Thanks.