Method 1

If you can, please get a monitor with VGA port. Then please connect DVR to monitor with VGA cable to test if you can see video on moitor.

If you can see live video on monitor via VGA cable, go to Main Menu--System--Display and changed resolution to lower one. Finally, you can find HD TV can see live video.

Method 2

Please check if computer can detect DVR's IP and access system. Here is method:

https://hview.kf5.com/hc/kb/article/1032692/?from=draft

If it works, please change display resolution to lower one. Finally, you can find HD TV can see live video.