We identified the problem regarding the inability to download videos from YouTube and fixed it now. YouTube made some changes on their end so it broke our Downloader's compatibility. Here is what you should do to update the Downloader.
1. Using Chrome, Firefox or Edge, go to YouTube.com and play any video and click the Downloader button. (This action may still show "Unable to download" message)
2. Close all Windows,
3. Restart your PC.
Now try downloading your video. If the issue persists, please let us know.