After music deleted and upgraded to OS, I can no longer re-upload the same tracks that were on my Iphone prior to deletion and update.

Running Windows 8, latest version of Itunes (just updated last week).

Have Iphone 5, latest iOS update 8.3

Here's what happened:

-Needed to update to iOS 8.3. Not enough room on I-phone. So I deleted all my music to make room for the update.

-Did update. No problems

-Connect to I-tunes, try to re-upload the music I had on there before. Nothing happens.

-I try a song that was not on my Iphone, prior to the music deletion from Iphone, and the track syncs just fine.

-NONE of the tracks that were on my phone pre-update and pre-deletion can be re-uploaded onto the phone. I get no error messages or warnings: they just don't sync.

Why is this happening? Why are songs that were on my phone, then were deleted, unable to be re-loaded onto my phone?