I should have noted before that in order to use the downloader (or any downloader) you must have member access to the content to begin with.
DaHuman
Sorry I don’t have direct experience with that site but I know others have reported that same issue over years. The only suggestions I can make is to make sure you’re using the latest “yt-dlp” version and not the original/outdated “youtube-dl” version, then try using the “–cookies-from-browser” option for yt-dlp to try bypassing the need to create a cookies file, then finally try using the actual “–username USERNAME –password PASSWORD” authentication options. And as you mentioned, per this Cookies Guide some addons may require you to configure it to export the cookies in a valid format, but that’s all I can come up with.