Have you tried turning on advanced logging?
-debug -debugscripts in launch options (via steam). This will give you more information in the error.log file.
Code:
namespace = domuit
character_event = {
id = domuit.1
title = EVTNAMEDoM
desc = EVTDESCDoM
picture = GFX_evt_comet
ai = no
trigger = {
has_landed_title = d_vasconia
has_landed_title = k_visigothica
NOT = { has_character_flag = Domuit }
}
mean_time_to_happen = {
months = 1
}
option = {
name = EVTOPTADoM.1
set_character_flag = Domuit
prestige = 200
}
}
Also that event alone won't popup when conquering a duchy, you'd need to turn it into an on_action. Right now it'll just fire very regularly for a player that holds both the kingdom of visigothica and the duchy of vasconia.