I have been fighting the sim for a while for the AOE talent loadout because my DISC is still better than the belt I had in inventory although your sim disagrees. Now the sim refuses to equip either belt even though I’m willing to wear the discount mail-order belt (i upgraded it even though I had better gear to upgrade). If I don’t pay attention I end up not wearing a belt when I go into a dungeon. Help!
So you have a lot of locks and exclusions… and it is painting the optimizer into a corner. The main issue stems from the fact that you have locked a unique gem on your neck, and also on your DISC belt, and you also have excluded all but one neck item option, and locked in the DISC belt as well.
There is no way to give you a solution that obeys these locks, exclusions, and is also valid (doesn’t violate the gem unique constraint).
You can start by unlocking the gems on your neck item and then re-optimize. Then the DISC belt will show up again that you have locked in place. That might be all you need to get what you want.