no connection available on NBN Router or on WI-Fi Dongle other device can connect to both networks

I have an older Apple TV (4yrs old) i have had no problems connecting to NBN network until two days ago, The message I get on TV is "Your Apple TV isn't connected to the network, Check settings" i have done this and the Apple TV searches for the network but cannot find it. I have tried connecting to my WI-FI dongle that used an other provider as well as my mobile phone hot spot and changed the HDMI cable no joy.The other devices, 3 PC, 2 IPads and two mobile phones can connect to my NBN network and the WI-Fi Dongle.