Car compact disc (CD) players are mechanical devices unlike current music players (MP3 players) and even unlike the basic car radios of old. Technologically the product's timeline fits in the middle between two solid state eras---the analog radio and the computer. The CD isn't particularly well suited to cars because the mechanics are susceptible to vibration. However, they hold up much better than the technology they replaced---the music cassette.
Make sure the CD can be played in the player. Generally, neither small 3-inch CDs nor strangely shaped CDs that are not round can be played. Look for the "Compact Disc" logo because CD players often won't play discs unless they are a certain specification. The "Compact Disc" logo indicates that the disc meets the criteria. Car CD players often can't play home-made CDs. Check the specifications for audio files. Check that the method for reading the CD matches your CD. There is often a setup menu item called "CD Read" where you can switch between audio file CDs and music CDs. Check the manual for instructions on how to set this.
Check that the number of CDs you have inserted into any CD changer matches the number of discs the CD changer can hold. For example, a six-disc changer can only hold up to six discs. Any more will jam it.
Make sure you are pulling the CDs out of the player horizontally if the CDs are getting damaged.
Check that the CDs aren't dirty. Clean CDs from the center outward with a soft cloth. Try a CD player cleaner disc.
Check that the CDs aren't scratched. Replace the CD if it's badly scratched.
Make sure that the CD player is not in store demonstration mode if it's the first time you've used it and it's not behaving as you would expect. Consult the manual to see how to disable the demo mode.
