After some more investigation, I’ve determined that the basic problem is that Sermon Browser is inserting a into the wp_sb_sermons table, but there is no corresponding entry for the file in the wp_sb_stuff table. By inserting into wp_sb_stuff an entry which links to the wp_sb_sermon entry, I was able to make it to work properly.
This is obviously not sustainable, but it hopefully sheds some light on what might be happening. Any ideas?
Thanks!
If it helps, I’m running WordPress 4.9.6 on PHP 7.2.