In case you have the same issue. It turns out the iPhoto app won’t run on Yosemite. The new photo app is called Photos with a new app icon. This is how to fix it.
1. Make sure in your osx App Store app, there is iPhoto under Purchases
2. Open Finder, delete your iPhoto app. (You will probably need to put in your admin password). Don’t clean up your trash can yet.
3. Then restart.
4. Once log back in, open App Store, go to Purchases, install iPhoto. It will take a while to download.
5. The new app is call Photos with a circular icon. Once verify you could clean up your trash can.
Hope this helps! =)