New MacBook Air won't sync photos from iCloud

I love my new MacBook Air after finaklly moving away from Windows but am really frustrated as I cannot get photos to sync from iCloud:

1. iCloud is on for everything I want EXCEPT photos. I will not allow me to toggle the button on for "sync this mac"
2. When I open Photos there are no photos and am greeted with "The library “Photos Library.photoslibrary” could not be recognised."

Any help would be greatly appreciated! Thanks