Okay, so…
I inspected the wp-content folder and found no “uploads” folder. I uploaded the original “uploads” folder with no joy.
I checked the settings-media page and found the media file path was wrong (it was missing the “public_html” directory. I fixed that. No joy.
I re-uploaded the “new” image, confirmed that it was in the right directory. It now displays on the “test-image-page, but still an icon in the media library.
I installed “force regenerate thumbnails” plug-in and ran it. It got 1 success (the new image I just uploaded) and 8 failures (all the original images).
The thumbnail for that image in the media library is still an icon.
I tried editing the “test-image-page”, re-inserted an old image in the “older image not rendering” section. It still doesn’t have a file name (although the path is right).
Now, some images are showing and some aren’t.
What the heck is going on?