Hi,
I have exact same issue. I can see only 3 out of 4 cameras in the app. The one that appears as unavailable is alwasys the one added to the 4th poe port (out of 8), no matter which camera is. I tried to add to different ports, but no success.
DS 7680NI-K1-8P, encoding 265+, firmware v3.4.110...