1. Incomplete disc information or scratched disc.
This is the main reason for the issue. Before you try anything to examine or fix your DVD player, it's suggested that you make sure the disc you are trying to play is intact and well. If it's the problem of your disc, then trying to fix your DVD player does not help at all. In this case, you can copy the scratched DVD disc
and then you may play it on your player machine.
2. The disc is incorrectly formatted.
A common DVD disc or Blu-ray disc is formatted in various ways. You can find different DVD or Blu-ray disc types in the market, such as DVD-RW, DVD-R and 4K Blu-ray disc and so on if the disc is not formatted correctly in accordance with the player, then it will not be detected. You can use some software tools to correctly format your DVD disc
3. The glitch of the DVD laser lens.
Most of the DVD "No disc" problems are caused by the glitch of DVD laser lens. The cleaning DVD laser lens is not easy and requires patience and carefulness. You can start out by trying to blow away the dust if that doesn't work, you can try using a DVD cleaning disc.