Hello Izadi Gazar Mohammad
Welcome to the Microsoft Community.
If you can access other websites without problem, but just cannot connect to Riot server in Australia, it could be due to some blocks between the server and your local network. You can try changing to another network environment, such as a Wi-Fi hotspot provided by your phone. Besides, changing a different DNS server might work. Tap Windows Key+R and type ncpa.cpl. Click on the name of the network you are now connected to, open the Network Status window, click Properties, and then double-click Internet Protocol version 4 (TCP/IPv4) in the Network Properties window.
Manually set the DNS servers to "4.2.2.1" and "4.2.2.2" and restart the computer to see if the problem is solved.
If you still cannot connect, you should contact Riot support to report the problem. They may have more professional advice on this issue.
Best Regards,
William.Y | Microsoft Community Support Specialist
