The "We apologize for the inconvenience" message is caused by an outdated version of youtube-dl.exe (found in \YouTubeRetro\ytretro_Data\StreamingAssets\bin), and you can just download and replace it with the newest version from https://rg3.github.io/youtube-dl/download.html without much trouble.
It's worth it, in my opinion--this is a beautiful, atmospheric project.