...ialogue though.

So I dump the player into a cell and have a scene that makes the player walk towards an NPC while the NPC uses a ForceGreet package to walk towards the player. The scene works, until the part where the NPC is supposed to forcegreet the player. He walks up to the player, then stands there and doesn't say anything. A debug notification on dialogue start doesn't trigger, so clearly the dialogue is never launched.

If I remove AI control over the player and walk over to the NPC, I can then press E and launch the conversation manually: the NPC starts saying the blocking topic and the conversation proceeds as intended. Walking away from the NPC after he stops does cause him to follow me, indicating that his forcegreet package is still active.

If I remove the package from the scene and just give it to the NPC naturally, the same thing happens.

I'm aware of the Start Game Enabled bug, which is why I'm using another dummy quest that launches this one 2 seconds into the game. (Edit: generated a SEQ file anyway, no difference)

I'm at wit's end. What do I do?

Since you aren't getting any dialogue or debug messages, I would expect that the issue lies with your topic definition in the package. Are you using the default Force Greet package, or did you make your own custom version? The default needs to be linked to your quest and that quest must have a 'hello' topic for this NPC to speak. Are you sure the conditions on the topic are set correctly for this NPC? One way to check is to load up the NPC in the CK and hit the Dialogue button and check if your hello topic appears in the list. If it's not there, then you most likely have condition issues with the topic.