MAC address filtering
If your router uses MAC filtering you need to temporarily disable it to find the MAC address of your own Petcube Camera. This can be viewed in the list of connected devices in your router settings. Once you have its MAC address, you can safely add your Petcube Camera as an exception and turn the filtering back on.
If you're using an iOS device, you may also find useful Fing app from the Appstore or if you're on Android, then Wi-Fi Analyzer will help you finding its MAC address.