Use the following steps to resolve this issue;

1. Confirm if the camera can be watched on surveillance station. 

2. If you can watch from Surveillance station, Using Project Documentation (RACK ELEVATION DRAWING, SINGLE LINE DRAWING) confirm if the camera are connected to NVR or directly to the Switch.

3. Power Cycle the Network Switch.

4. Escalate to Technical Support Officer.

The Issue may be caused by ;

1. Camera may be offline.

2. Network switch or NVR powering camera may be switched Off.