[Plugin: Last.fm Post Extension] Stopped working

I am using the Last.fm Post Extension and it just suddenly stopped working. The plugin is the recent version, I haven’t edited anything, the code is still in the template. And my scrobbler is still scrobbling.

You can see it worked and showed up here:
https://www.morbid-romantic.net/2009/03/28/in-the-mail-0327/

But on none of my most recent entries:
https://www.morbid-romantic.net/2009/03/30/in-the-mail-0330/

I know that the Last.fm client was just updated the other day (I just upgraded). Does this have something to do with the plugin suddenly no longer working?