Emoji & Symbols panel no longer appears

I have been using the Emoji & Symbols panel quite often for years, but in the last few days it does not appear when summoned. The icon is in the menu bar and the Show Keyboard Viewer item works.

If I hit Cmd-Opt-SPC any number of times the Edit menu item flashes each time, but no symbols panel appears. I checked all the "spaces" in case it somehow got stuck in one of them.

If I use Edit>Emoji & Symbols, nothing happens.

If I use the input menu's Show Emoji & Symbols item, it alternates between Show and Hide each time, but no panel.

I've tried all the above while the current application is Chrome, Calendar, Mail, Terminal, Discord, and several others.

I tried $ killall Dock which was no help. I have not rebooted and hope I don't have to.

10.15.7