Songs gone on iphone after adding more music with app

My songs are gone on iphone after adding more music with the "Music" app on osx. The new songs are there, but the older songs are gone. But when I check the "Music" app on my macbook, it says the older songs are still there on my iphone, it just does not show up on my iphone. This happens every time when I add new songs to my iphone from the "Music" app on osx.

ON MUSIC APP ON OSX:

ON IPHONE: