Smart Wired CCTV allows access to main menu but no images are shown

Make sure the connectors are securely in and do the following:

Check the power supply to the cameras.
Check that you are viewing the correct channel.
Make sure you have followed the initial set up wizard.
You can reset the DVR in factory mode and restart the process again.
Go to System in setting menu, select “Default” menu option on the left side menu and then press “Factory Default”