this happens to me as well, it takes ages to load and displays that page. Normally it is fixed by refreshing the page. Also what browser are you using apparently there are issues with internet explorer and edge. Chrome or Firefox are recommended.
the play button plays a youtube video of the song and because of copyright the video gets taken down and the link doesn't play anything but if they use the official video from the official channel it should work.
I tried it out changing the tuning pitch from 220 hz to 440 hz (E standard) repacked it and when I played it it didn't pick up most of the notes and got 1.2% on it.