If it's a physical problem with the disk, one thing that has worked for me many times is rubbing alcohol and a microfiber cloth. Pour alcohol over the entire disk, make sure it covers everything. Then use the microfiber cloth to wipe it until dry. If there is any dirt/smudges causing the issue, this'll normally take care of it, and it's pretty safe if you are using the typical rubbing alcohol you'd get for use on cuts and such. On many things, I water it down first, but on CDs, I pour it straight on.
"But thanks be to God, which giveth us the victory through our Lord Jesus Christ." 1 Corinthians 15:57