Greyed out songs when trying to add from iTunes to iPhone?
Try playing the greyed out songs directly on your iPhone. If you cannot do that, do the following. 


Ensure that the greyed out songs are indeed playable within your iTunes library (not within the iPhone section of your iTunes library)
Connect your iPhone to your iTunes, navigate to your iPhone section > music, select all greyed out songs and delete them. 
Make sure that the "Sync music" and "Entire music library" options are ticked under the "Music" tab and sync your iphone once again with iTunes.


This should resolve the issue.