some songs are not copied from my itunes to apple devices (apple 5s ,apple nano) why??

Are they selected to sync to the device?

I have the same problem and YES, they are selected.

I'm having the same issue. I originally downloaded most of them via my phone. My wife downloaded some as well. I can play on iTunes but these few songs will not sync. I've bought music after those and the new ones sync just fine.

I'm having the same problem as well

Woo Hoo! Spent a long night with Apple Tech Support and finally got it to work. Try this:

1. Start iTunes and attach iPhone to your computer (duh)

2. Open your iPhone tab and uncheck "sync music" box. Click Apply. ALL YOUR MUSIC WILL BE REMOVED FROM THE iPhone so make sure you've transferred all of your purchased music to your computer first. Your blue bar (music) memory usage should go to zero, according to the technician that was helping me. Mine did not (5.68GB left) so we were worried that the data might be corrupted. However...I had no issues after the next step. Maybe it was left over podcasts? They used to be accessable via playlists (man, I miss that feature). No clue about that. But don't worry if you see the same thing.

3. After sync is complete (i.e. removal of all music), check "sync music" box and click Apply. ALL YOUR MUSIC WILL BE RELOADED TO THE iPhone

4. If this method does not work you likely will need to do a hard reset, wiping all of your data. You can attempt to back up your files prior to wiping, but don't save your music files since anything that is corrupted before the backup will be corrupted after the backup (garbage in/garbage out). Fortunately I did not have to go this far....

Good luck!