Version: MCFunction (Haven't tested Marshal Command Code)
Issue: instant_damage and instant_health are marked as invalid syntax. To recreate, simply do effect give @a minecraft:instant_damage or effect give @a minecraft:instant_health.
Screenshot showing that instant health and damage don't work but other effects such as night vision do:
Version: MCFunction (Haven't tested Marshal Command Code) Issue: instant_damage and instant_health are marked as invalid syntax. To recreate, simply do
effect give @a minecraft:instant_damage
oreffect give @a minecraft:instant_health
. Screenshot showing that instant health and damage don't work but other effects such as night vision do: