Unable to delete photos in my MacBook's Photos and download new ones.

My OS is High Sierra 10.13.6 and Photos Version 3 (3291.13.210). Yesterday I imported about 150 photos from my Nikon. I am able to edit them, but NOT delete them.

Today, after taking about 100 more photos I attempted to import them, but although it appeared they were being imported by the countdown clock, the photos did NOT import. I tried another camera and got the same results. When I tried again, I get the message that they have already been imported.

The pictures do not show up anywhere.

When I attempt to delete a photo, I get the pop up box saying "One Photo Deleted." but it isn't.

I have quit Photos, rebooted, turned off the Mac and nothing works.

The photos are being stored in my Library. NOT the Cloud.