Music playlist won't generate thumbnail image

I’ve just started using Plex playlists, and for some reason whenever I make a new playlist, the image for it remains blank and no thumbnail is generated for it. It worked fine for the first playlist I made, but all subsequent playlists will not generate an image.

I’ve tried restarting my server (hosted on my Nvidia Shield TV), and I’ve tried deleting the playlist and creating a new one with a different name. Yet Plex still won’t create a thumbnail for it. All of the songs in the playlist have album covers. I’ve read other threads on this issue and it looks like an update was released, but it doesn’t seem to be working. Any help would be appreciated.