The monitor's or TV's resolution must be higher than the recorder's display resolution.If not, monitor or TV is not able to show any image.
If?monitor or TV can't show any image at all and says not supported, it's maybe the recorder's is higher than your monitor's, which causes no image.
There are 3 ways to solve this issue.
Method 1: Please use a higher resolution monitor to connect your recorder so that you can log in recorder and change it's display resolution to lower one.
Method 2: Please access camera with software CMS on windows computer to change its display resolution to lower one.
You can refer to this link below to access system on CMS.
You can refer to this picture below to change resolution on CMS software.
Method 3: You can access recorder system on computer browser by recorder's IP and change its display resolution in web page. You can refer to this link below to find its IP and access it.