[Hopkins]

I just noticed I have the same problem. When I look at the "User Plugins" dialog window in the main program, I see that the plug is in the "Not Installed" list. But when I open the editor, I see that the plug is available (and works) under the "Plugins" menu.

Try this:

1. Select a book in the main Calibre program
2. Open the editor by clicking on the "Edit book" icon
3. Click on the "Plugins" menu item in the editor

Check if there is an entry called "Convert Chinese Text Simplified/Traditional".

It's possible that the plugin is actually installed, but not properly registering with the main library application. Let me know what happens.

Edit:

Also, try this in the main Calibre window:

1. Click on the "Preferences" icon
2. Click on the "Plugins" icon which is at the bottom of the newly opened "Preferences" dialog
3. Click on the "Edit Book Tool plugins" pull-down arrow

The plugin shows up in the list in this dialog in my case.