Q: fotos starts up but shuts down immediately

Hello elena295,

Thank you for using the Apple Support Communities. I know having the Photos app not work is not what you expect. If I understand correctly, you are unable to launch the Photos app on your Mac, as it will open and then quit right away. Here is what I suggest to resolve this issue:

1. First, try running a quick test with the built in Disk Utility tool, as this can correct simple issues like you're experiencing.

Disk Utility (El Capitan): Repair a disk

2. Use Safe Mode to start up your Mac so that it performs certain checks, delete system cache files, verifies your startup disk, and attempts to repair directory issues if needed.

Try safe mode if your Mac doesn't finish starting up
Limited graphics performance in OS X recovery or safe mode

3. You can figure out if unexpected behavior is related to user file or setting by trying to reproduce the issue from another user account. This process includes creating a new user account, logging in to it, and testing for the issue.

How to test an issue in another user account on your Mac

Cheers!