This push notification is sent when your CubeOne disconnects from the internet. There are a several common reasons that can cause this to happen:
Poor internet connection
Ensure your home's internet connection at the time you received this message was working without issues. Unplug the power from the bottom of the CubeOne for 20 seconds, then power it back up. Make sure the light at the top of your cube is breathing white.
Poor connection between the CubeOne and router.
Try using a different network cable or a different port that you've confirmed works without issues on your router.