Photos widgets say "No photos available" – macos Sonoma 14.0

The Photos widgets in macos Sonoma 14.0 display as gray with the words "No photos available."

The problem applies to both Featured and Album widgets.

Clicking on the desktop widget opens Photos and its default library. All content is present in the app and the app works fine.

I do not use iCloud for Photos. My library is stored on my machine.

The problem began before the Sonoma upgrade—I just didn't ask about it when I first discovered it.

At that time my library was stored in the Dropbox folder on my computer. Then Dropbox changed how it worked, including moving all the contents of the old folder to a subfolder buried in the Library folder. When all that moved, the Photos app demanded that I move the library out of Dropbox, that it couldn't/wouldn't access the library in Dropbox. So I did, putting the library back in the Pictures subfolder of my Home folder. Then the Photos app operated normally and I had access to my library.

But the Photos widgets stopped working, and they did not start working again.

I thought a future OS update might take care of the problem by itself, but it didn't.

Then I thought a major, named OS upgrade might take care of the problem, but it didn't either.

So now I'm asking for help.