To change the WiFi security settings log into the modem (http://192.168.0.1, password is Telstra), go to Advanced and then to WiFi, change the Security mode and save settings. By default modem is set to WPA2 PSK, the other setting is WPA + WPA2 PSK. Change settings for both WiFi bands.
If changing security mode doesn't allow Xioami to connect try changing Protected Management Frames (Wi-Fi PMF). If on turn off, if off turn on.
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