Missing photos since update
I updated to Sierra yesterday. After which, I returned to editing the new photos I just took, which had already been uploaded pre-update. When I opened up Photos to do so, I noticed that at least 80% of my photos had thumbnails with a grey triangle and an exclamation point. Once clicked on, some of the photos would show up. However the thumbnail remained as this triangle when i returned to the folder. I have tried to repair the library (⌘⌥ while opening) but that hasn't worked. I will add that I haven't used iPhoto since the last update so I don't think that has anything to do with this since several of these photos were imported straight from the source to Photos.
Can anyone help? I need to make sure I have access to these photos.
MacBook Pro (13-inch Early 2011)