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Look in General section in BIOS (could be elsewhere). Is your DVD detected as a device? It could have a problem. Switch off your computer, remove power and SATA cable from DVD and leave it for a few minutes. Connect the Cables again and go into BIOS. Can you see it? You can also try using a different power and/or SATA cable, if available.
If it is a notebook you can try to remove the screw holding it in place, remove it and place it again.
Select "USB CD" from the list and see what happens. How did you burn your DVD, are you sure its bootable?
If the internal DVD shows in BIOS but not in boot selection, then maybe boot from DVD is disabled in BIOS. Have a closer look. If it doesn't show in BIOS as a device, try to remove it and put it back. A bad connection can cause problems. It may as well need replacement.
On my laptop, if there is no bootable media in my optical drive, it does not show up in the quick boot menu. It's not listed at all as a boot option.
Set Boot Mode to 'Legacy Support' in Boot menu, don't forget to change it back afterwards