I have deleted and re-uploaded the images via FTP and the transfer goes fine and I can view the images in a browser window with their proper address, but the grav admin won’t acknowledge them.
I’ll chalk this up to a hosting issue. Even after logging out and back in to the admin, it continued to display those four thumbnails as errors so I gave up troubleshooting. This morning when I logged in, the thumbnails are there and displaying properly in the admin.
