Please check below information on the cameras in question and let us know the result via firstname.lastname@example.org.
1. Unplug the camera from power, wait for a while, then re-plug the camera back to power, see if it works.
2. Cover the camera lens with your hands and see if the camera's infrared lights turn on.
If yes, that means the camera is still work.
If no, please try with the power supply for a working camera see if it gets power.
3. Right click your NVR mouse, then click Device Manage, take a picture and send it to us.
4. Please tell us your order number and the model number of your item.