Try the following quick fixes if your CCTV security camera is not showing images:
1) Please check if your security camera power supply is working properly. You can cover up the lens of the camera, if you hear a click or see a red light in the lens, this would indicate if the camera is receiving power.
2) Test your security camera on a different DVR/NVR port.
3) Swap the input cables (BNC cable or Ethernet cable) to see if it makes a difference.
4) Confirm if the video formats that your security cameras and DVRs/NVRs support are compatible.
Please let us know if you need more help: