You can make the images in your Photos library available in other apps by following these steps:
- Make sure that your Photos library is set as the System Photo Library.
- Make sure that your Photos library appears as expected when you open Photos. If it doesn’t, repair your library.
- When you're able to access your Photos library in Photos, leave the app open overnight. The information in the Photos library updates in the background while the app is open. When this process is complete, you should be able to access your photos in other OS X apps like iTunes.