YouTube Downloader error

Hi all,
I am using DropZone 4.1.9 on macOS HighSierra 10.13.6 and I cannot upgrade further the operative system.

Until a couple of days ago the Youtube downloader script worked fine, then I probably updated the script, I'm not sure, and from that moment when I try to download a youtube video I get this error:

[Launching task with command line: runner.rb task-91115]

Task description file task-91115:

ACTION: "/Users/xxxxxxxxx/Library/Application Support/Dropzone/Actions/YouTube Downloader.dzbundle"
EVENT: "dragged"
VARIABLE: "path" "/Users/xxxxxxxx/Downloads"
VARIABLE: "dragged_type" "text"
VARIABLE: "tmp_folder" "/var/folders/4k/pf1bdrvx7yxdnnclxfndfny80000gn/T/"
VARIABLE: "app_version" "4.1.9"
VARIABLE: "support_folder" "/Users/xxxxxxxxx/Library/Application Support/Dropzone"
ITEMS: "https://www.youtube.com/watch?v=xxxxxxxxxxx"

Traceback (most recent call last):
  File "/Applications/Dropzone 4.app/Contents/Actions/lib/python_runner.py", line 7, in <module>
    import action
File "/Users/xxxxxxxx/Library/Application Support/Dropzone/Actions/YouTube Downloader.dzbundle/action.py", line 17, in <module>
    import updater
  File "/Users/xxxxxxxxx/Library/Application Support/Dropzone/Actions/YouTube Downloader.dzbundle/updater.py", line 38
    print(f'Latest version: {version_id}, Current version {current_version}')
                                                                            ^
SyntaxError: invalid syntax

[Task completed]

I tried to delete the app and retrive from a Time Machine backup, deleted the folder Dropzone 4 and Dropzone in Library/Application Support, reinstall the action from the website, but with no luck.

What can I possibly do?

Again, no chance to upgrade the macOS, everything worked until few days ago.

Thanks so much.