Do you have the main campaign Story as a data dependency? The useful Osiris document only describes systems implemented in the main campaign. If you have a mod that's from scratch you have to implement this yourself. Either by copying code from the main campaign, or by writing your own system.
The other possible cause is that your Database entry is being added before the goal that handles DB_Dialogs has been made active. Check the name of your goal and make sure it appears AFTER _PROC in the story.div file.
The _PROC goal is parented to _Start, so make sure your custom goal is parented to _Start as well. There was an issue with parenting to _Start for mods, so in case that doesn't work for you, make a new goal called _ZMod_Start that has nothing in it but:
IF
GameEventSet("GAMEEVENT_GameStarted")
THEN
GoalCompleted;
and parent to that goal instead. This will make sure that any code you add for your mod will be activated when all the Main campaign code is active.