One reason a DVD player cannot read a disc is because the disc is scratched. Smudges and fingerprints can also prevent a DVD player from reading a disc.
If the disc in question has smudges or dust, a soft cloth should be used to clean it. Users should wipe the disc in sections from the inside out to prevent further damage.
A faulty device can also prevent a disc from playing. To determine if this is the problem, users should insert a different disc to check whether or not it plays. If the new disc fails to play, the DVD player may be faulty.