I debugged this and the plugin works. But for some reason, when the plugin checks the newly opened file for comments and to look for keywords, there is no styling set yet in the Scintilla object. And since there is no styling set, the plugin finds no comments at all (https://github.com/geany/geany-plugins/blob/master/addons/src/ao_tasks.c#L58...) and skips the line.
This has been working in the past. I wonder if there was a change in Scintilla so that configured styles are applied asynchronously (in a separate thread or so) and so the plugin searches for styles before they have been applied.
This particular case can be fixed by a `g_idle_add()` callback. But I wonder what else might be affected by this, there are probably more plugins and maybe also Geany directly affected if this is the actually the case.