I like this plugin a lot, but it seems like the quests either don't update at random, or get erased when new ones are added. I'm not sure if I'm doing something wrong or if there's a bug.
If it happens when you load a game and don't open the questlog before adding a new quest then it's a bug, it has been just reported and a fix will come in the next few hours :)
If that's not the case then be sure to use differents ID for the quests ;)