Please make sure all cameras have been connected to video-in ports of recorder with cables and recorder has been connected to?a monitor or TV with a cable, but there is no live video of all cameras?shown on monitor (You can still see recorder's setting interface ) .
Please refer to these ways below to have a try.
1. Please refer to this link below to check if you connected your system correctly.
2. Please go to Main Menu---System---General to change Video Standard. If it doesn't work, change it back to previous one.
3. Please use hands to cover the front of camera. If you can see infrared lights turns on with red lights like picture below shows, cameras are on.
If all cameras are not on,
3.1 Please connect adapter to one camera directly without 1/4 spliter because maybe spliter is broken.
3.2 Please connect adapter of DVR to one camera directly without 1/4 spliter because maybe the cameras' adapter is broken.The adapter of DVR can be used to connect camera.
4.Please go to Main-Menu-Advanced to click Restore to reset recorder to factory default.
5.Please go to Main Menu--System--Digital--Channel Type to confirm the first option is ticked.