I can't get AUDIO First using Google Chrome then using Mozilla Firefox to the download : https://www.youtube.com/watch?v=PLdRpX2nn2g&t=290s
Do you mean the video has no audio in it?
Downloads and plays back here ok.
Simply enter the url as above and hit enter (or the down arrow).
Ensure your using a good player like VLC. Depending on what format/qualities/codecs you choose to download you may need to use the built in converter to convert to codecs that not so good players support.
If your still having issues please provide debug logs using the following instructions.