AI sight system erroring for no apparent reason?

I've recently been working a game that needed a smarter AI, and the only one I could find has one function that always errors for me, even though I directly copied it after it errored the first time, it still errors though

this is a normal script in a model in the workspace

function CheckSight(target)
	local ray = Ray.new(MyRoot.Position, (target.Position - MyRoot.Position).Unit * 40)
	local hit,position = workspace:FindPartOnRayWithIgnoreList(ray, (script.Parent))
	
	if hit then
		
		if hit:IsADescendentOf(target.Parent) and math.abs(hit.Position.Y - MyRoot.Position.Y) < 2 then
			print("visible")
			return true
		end
	end
	return false
end

it always says "unable to cast object to value", but it worked just fine for the guy who made the original script.

so if anyone has any idea why its erroring, please tell me, I'm trying to have the game out this year (bad idea, but it was my brother's idea not mine)

thanks for the help, I never would have noticed how the brackets were the wrong ones :) although the ray system you said I should change doesn't seem to error at all, so I'm just going to leave it as it is for now, and if it starts to error, then I'll change it.