Some mp3's not playing

I’ve been using this plugin for a long time and really love it. But suddenly today the sermons I have uploaded aren’t playing. They are the same as all of the other sermons that have been uploaded. No differences at all. Any ideas why these aren’t working?

Top 2 on this page:

http://www.sthelenas1712.org/sermons-and-classes/classes/

https://wordpress.org/plugins/sermon-manager-for-wordpress/