Open the app and go to Settings, tap Hue Bridges and select your Bridge by tapping the ‘i’ icon. Tap Zigbee channel change. Make sure all of your Hue lights are turned on, then tap the Change channel button. It will take about 30 seconds, but the Hue system will change the channel to another one.
Once done, your lights should all come back online. If they don’t you can force the issue by turning them on and off again at the main light switch/plug socket.
Source
