mp3 files not read

Can anyone tell me why, all of sudden, whenever I insert a CD-R containing mp3 music files it is not automatically read and recognized? I never had this problem until very recently. Previously, I would simply insert a CD-R and, after several seconds, a box would appear onscreen telling me that the mp3 files were ready to access. Now, however, I put a CD-R in and nothing at all happens. I can't figure out what the difference is. Perhaps I need to change a setting. I feel that there should be a simple solution. Thank you.

Bill