"An Object Could Not Be Cloned" - is this still being maintained?

[gotofritz]

Hi, thanks for the plugin, but it doesn't seem work anymore.

Using: Calibre 8.5.0
Joplin: 3.3.13

I select "File > Import > CLDB ..." and I select the folder where the library is stored.
The plugin throws alert "An Object Could Not Be Cloned" and quits.
The same if I select one of the book folders within the library.
The import dialog doesn't allow me to select the metadata.db file directly.

Am I doing something wrong or is this plugin no longer functional?