For a quest in my mod, I have made a character jump out of a bush and greet the player.The only problem is that I can't actually get him to say the dialogue. He jumps out of the bush and then promptly tells the player he has no greeting, then walks off.

I've added the initial greeting I want to the GREETINGS topic, with the conditions GetIsID [Speaking NPC] and GetStage [Quest] [stage], but he still refuses to say it. I've checked and double checked that I've reference the right NPC, and even rebuilt and re-referenced him, all to no avail.

Is there something fundamental I'm missing here?

Just a thought, but have you moved the topic to the quest? Also, recheck the GetStage etc, might have made a boo boo there.