When reporting back to Hannibal Traven after getting the black soul gem in MG17Ambush, GetStage = 90:
Dialog Topic, Greeting should be, "Were you successful? Do you have the Black Soul Gem?" The condition is wrong so you don't get this dialogue.
Conditions are:
#0 Equal to 1, GetIsID HannibalTraven
#1 Equal to 30, GetStage MG17Ambush => change from 30 to 90
Stage 30 dialogue result = "Go. Find Thalfin, and the other Battlemages. Stop the gem from reaching Mannimarco." (incorrect for the stage)
Stage 90 dialogue result = "Were you successful? Do you have the Black Soul Gem?"