Make sure that Casambi enabled luminaires are powered on, and your mobile device’s Bluetooth is on as well. Please also make sure that you've set the "Bluetooth luminaires enabled" option on in the Casambi app's "App settings".
To be able to access previously created networks that are stored in Casambi cloud server please make sure your mobile device has access to internet. 'Location' is also required for newer Android devices for the Bluetooth to work properly.
If no luminaires are found, they might be paired to some other network. Please open "Nearby Devices" screen and see if the luminaires are listed in there. In Nearby Devices screen, you can see if the luminaires are paired or unpaired. If they are paired and you want to use them in some other network, then you need to unpair the luminaires first.
If you have a Philips HUE gateway please make sure your mobile device is connected to Wi-Fi, and you've set the "Philips Hue enabled" option on under "App settings" in the Casambi app.