There must be something wrong with my download.
Clicking on the X at the top right corner of the screen did not shut Joplin down.
Clicking on the Exit item under the File menu did nothing either.
So I went to the Control Panel and discovered I somehow had 4 instances of Joplin running. The only way to shut them down was to "End Task".
It took six tries this afternoon to download the Joplin install file. Grant you, it's an old computer. I thought perhaps on a cold, snowy Sunday afternoon that the local internet connection might be slow. I will try again tomorrow, once kids are in school, and see what happens.
Weird!!
Monday morning: I just uninstalled Joplin (Version 2.5.12), then tried downloading it from a different source (SourceForge). It took a few tries to download the setup file, but ultimately, the result was the same as before. Joplin screen shows up, but under the File menu, only the option of "Exit" appears.
Clicking on "Exit" does nothing - no exit, nothing changes.
Unless someone has a bright idea, I guess Joplin is out and Obsidian is in.
Thanks for any help.