I just had this issue on the app, but after about an hour of playing with the app I found the solution (at least for me). At the very top of the app (above the modes) in the middle there should be your Location with a drop down button (I have it saved as Home). If you click that drop down, it'll show you all the locations on your account. If by chance you installed the new item under a new location, you'll have to click on that location to see the camera. I unistalled the device, and reinstalled it using my same location (Home) and now I can see both my cameras without any issues.
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