Ideas
I had this happen to me as well. My sim, a teenager fairy died of urban myth. I then make her a playable ghost and notice, nothing happen when she died for the will to be executed. So the heirloom she had selected to be given to a family member is no where to be seen, the message and emotion she left also never got displayed... not sure of sims are supposed to get the Will a certain way and read it for this to happen, but I havent received mail or notification for that matter. After her death, she had her will in her inventory, with the only option to Destroy the Will. I gave her ambrosia, turning her back to live and she also only had the option to destroy the Will... after I Destroyed it, I tried to create a new one and it was not possible, like everyone else here on this topic, saying that she already had one.
I have all DLC and don't use mods.