What did I do wrong? No thumbnail previews?

For some reason I don’t have the video preview thumbnails anymore? What have I screwed up? Thanks.

The feature itself seems to be working fine.
You could have disabled the creation of preview thumbnails on the server side or deleted the existing ones from the advanced library configuration.

It started working again. What I think happened was that I had to delete Plex when I updated my DSM on my Synology NAS. I think it just hasn’t had time to redo all of the thumbnails. Who knows, it is working again.