This article is about the VX1 Video Doorbell

AC Power

Like other parts of your security system, the doorbell can be affected by connection problems on the premises and outside, as well as simple issues like failure or disconnection of its power source.

Remember:

When power is restored, it will take a few moments for the device to reboot. Reconnection to Wi-Fi should take place automatically. 

Is the doorbell in Privacy mode?

If the doorbell is in Privacy mode, you won’t be able to view its stream. Recordings will not be triggered by motion or sound detection, nor can video recording and still pictures be triggered manually.
 
You can turn Privacy off and on in the apps, as seen here…
 
…and on the website, as seen here:
 
 
Privacy mode does not affect the camera’s Power or Wi-Fi connectivity, so the camera should work again as soon as Privacy mode is switched off.
 

Has the camera been deleted accidentally?

On the apps and the website, each camera’s controls include the red text button DELETE CAMERA. If touched or clicked accidentally, any camera be deleted from your system with just a couple of touches or keystrokes. For more information, see the FAQ How do I delete my VX1 Video Doorbell? (And why would I want to do that?)