Here is the workaround as I have been facing the same issue for many months now, and no new fixrelease has come since.
Follow the steps from Filip here:
in order to patch the GUI of our favorite tool.
(with admin rights)
find the line :
osHttpRequests.download('http://www.opensubtitles.org/en/download/file/%s.gz' %sub.getIdFileOnline(), destinationPath)
and replace it with:
Save and Enjoy