Why does my humanoid don't take Damage?

I would recommend checking from the server to prevent exploiters and you should probably make sure the leaderstats are loaded by using waitforchild instead of just going straight to plr.leaderstats.Reality

local Players = game:GetService("Players")

game.Players.PlayerAdded:Connect(function(player)
	local PlayerMoneyValue = player:WaitForChild'leaderstats':WaitForChild'Reality'
	player.CharacterAdded:Connect(function(character)
		local Humanoid = character:WaitForChild'Humanoid'
		while true do
			task.wait(.05)
			if PlayerMoneyValue.Value >= 0 then
				Humanoid:TakeDamage(10)
			end
			if Humanoid.Health <= 0 then break end
		end
	end)
end)