Cannot download photos from iCloud to Windows 10 computer

I used to be able to open the iCloud folder on my Windows machine, select photos, and drag and drop them to folders on my Windows machine. However, this no longer works. When I try to download, either by dragging and dropping, or by selecting a photo in the iCloud folder and then in Picture Tools choosing "Copy To" and selecting a folder on the Windows machine, I get this message:

"An unexpected error is keeping you from copying the file. If you continue to receive this error, you can use the error code to search for help with this problem.

Error 0x800701AA: The cloud operation was not completed before the time-out period expired."

The availability status on the file is "Syncing." But it never syncs -- I only see the file with a cloud icon.

If I try to log into iCloud for Windows, I get a "signing in..." message that spins and spins, but I am never signed in.