For some stupid reason I can't figure out, none of my aliases are filling. Is there a debug or something I can somehow run to determine why they're not filling? Everything looks right to me in my quest. They're only NPC's set as essential and to allow disabled. It's pretty straight forward. But in game I use the console and "ShowQuestAliases MyQuest" and they all show NONE. And I try "SetQuestAliases MyQuest" and it just says failed. I also have my quest set to warn if aliases don't fill, and I'm not getting any warnings.

Try setting them all as optional and see if your quest actually starts. If it does you can find out which alias is to blame by marking them unoptional one by one. If it doesn't you'll know there's a different problem with your quest.

This happens a lot with vanilla NPCs if you aren't marking your own aliases as "allow reserved". An NPC reserved by an alias will cause aliases in other quests to fail being filled.

Optional won't necessarily help if it's a reserve issue. So far as i know it hurts nothing to allow reserved. Then again, I don't fully understand the purpose behind it either.

if your alias is pre-filled using Unique Actor type, the actor reference itself needs to have a persistent location or else the alias will never fill.