Does autoadd work on thin client? (Deluge 2.0)

[nemonein]

Hello.
I'm using deluge 2.0.3 on Ubuntu server(20.04) as a server, and on Kubuntu(20.04) as a client.
I want to use the plugin 'autoadd', but I could not add watch directories.

I tried to add Watch Folders, but during addition, on "Watch Folder Properties" window, there's no reaction when I clicked the 'Add' button.
I entered the directory on the server as well as client's directory, both do not work at all.

Any suggestion will be appreciated.