Photos App: iPhone Photos not showing up when attempting to import
When I plugged in my iPhone this morning, it asked me if I wanted to share my photos with this device (meaning my computer). I clicked on "Yes", and the problem was solved. 

I thought the problem may be one where my iPhone didn't trust my computer to share the photos, but I couldn't find anything on the iPhone or my Mac. I checked iTunes too, but didn't see anything.

Once I gave my Mac permission to see my photos and everything is now fine.