During the standard installation flow, the network credentials are transmitted to the camera using a QR code.

Please ensure that the full QR code is visible on your phone while showing it to the camera, as well as brightness of the phone is high enough to make it easily visible. Also, please ensure you have enough lighting around you so that the camera is not in night vision mode and can clearly see the code.

It can be good to move slightly and slowly the code at different distances from the camera in order to ensure it gets a good grasp of it.

Note that QR codes are only valid for a certain time for security reasons. That way, even if someone has your Qr code, they would not be able to install additional products in your WiZ home. 
For this reason, a countdown is applied on the code. If the code is not valid anymore, you can generate a new one to try again.