We resolved an issue with the Downloader back on 28th April, 2019. Can you please follow the steps from the below link to make sure you have the latest version.
Something goofy today. When I tried to download a youtube video with my usual Chrome browser, I received an "unable to download" message. Same thing with my backup Firefox browser. Same thing when I opened RealPlayer, clicked on the 'download a video' button and pasted the URL in the box. But when I opened my ancient I.E. browser or the Microsoft Edge browser (both of which I try to avoid like the plague), the download worked fine!