itunes-ipad sync

hi.

I have an ipad air 2 with ios 9.0.2 and last version of itunes. I am trying to sync the music in my library (on itunes) in to the ipad, and the following is happening:

- after selecting the requested songs itunes start sync.

- in the ipad I can see song going over, as usual.

- when itunes end the sync process I can see all songs disappearing from ipad.

someone has any idea?

I have always tolerated itunes because did not have time to find an alternative, but this is too much.