NO DVD disk?

I have got a TECNOSONIC tv. My problem is that if I put inside a dvd disk - original and written disks - than appears on the screen - NO DISK.

I do not know why & I do not understand this situation.
How can I solve this problem?

It causes maybe no correct region?

I tried to change this but when I looked for this menu it did not want to appear on the screen

Many thanks for your help!