Unable to cast string to bool, What?

I'm making a game and I have ran into an error I don't understand Unable to cast string to bool

here's the script:

game.ReplicatedStorage.Remotes.BuyDance.OnServerInvoke = function(plr, Up, Down, Left, Right)

local animation = game.ReplicatedStorage.Animations:FindFirstChild(Up, Down, Left, Right)

if plr.leadersats.Points.Value >= animation.Price.Value then
	if not plr.playerValues.Animations:FindFirstChild(Up, Down, Left, Right) then
		plr.leaderstats.Points.Value -= animation.Price.Value
		
		local valUp = Instance.new('StringValue', plr.Animations)
		local valDown = Instance.new('StringValue', plr.Animations)
		local valLeft = Instance.new('StringValue', plr.Animations)
		local valRight = Instance.new('StringValue', plr.Animations)
		valUp.Name = Up
		valDown.Name = Down
		valLeft.Name = Left
		valRight.Name = Right

		plr.playerValues.UpAnimation = Up
		plr.playerValues.DownAnimation = Down
		plr.playerValues.LeftAnimation = Left
		plr.playerValues.RightAnimation = Right
		
		
		return 'Success'
	else
		plr.playerValues.UpAnimation = Up
		plr.playerValues.DownAnimation = Down
		plr.playerValues.LeftAnimation = Left
		plr.playerValues.RightAnimation = Right
		
		return 'Equip'
	end
else
	return 'Error'
end

end