You may be missing the iTunesHelper? Check your login items and if it's missing this should put it back:
1. Go to your Applications folder, show by icons, and select iTunes.
2. Use the Gear icon on the tool bar to get to Show Package Contents
3. Open the Contents folder with a double click
4. Now do the same with the MacOS folder
5. Locate the iTunesHelper icon.
6. Now open up your System Preferences.
7. Select Users & Groups and for your account click the Login Items tab.
8. Back to the iTunesHelper icon, drag it to the Login Items window.