Two other things....
Are you making "audio" CD's or "data" CD's?
Also, are you finalizing the disk?
Data CD's will not play on a regular CD player, and if you don't finalize the CD, usually computer CD drives will still read it, but regular CD players won't.
micmac has the other idea that I had too.
Oh, the only other possible one I can think of is that some older CD players will not play CDR's. This is a rare case though. Also, there are still a few not so old portable CD players that will not play CDR's.
Check all that out. I am sure one of them is the culprit here!
Good Day!