Humanoid isn’t the controller for animation tracks. You’d need to create an Instance, Animator, then parent it to the humanoid - hence, use that instance for loading animation.
it should still work when you call :LoadAnimation() on the humanoid
If the animation isn’t yours or the owners then it wouldn’t play either way unless you re-export it and play it with that id
if the game isn’t published in a group, then the owner has to publish the animation themselves for it to play (only plays in a live roblox game, not in studio unless you’re the owner)
if the game is published in a group, the animation has to be published to the group, then both developers and owners will be able to see the animation regardless of whether they are in studio or ingame
:LoadAnimation() for Humanoid is deprecated - therefore, it’s strongly not advised to utilise it to assure that the animations won’t break in the near future, or now.
local anim = Instance.new("Animation")
anim.AnimationId = "rbxassetid://6964312367"
local controller = script.Parent.Humanoid.Animator -- You need to utilize the Animator in the Humanoid
controller:LoadAnimation(anim):Play()