Unable to cast value to object? I'm having trouble with region3?

I'm trying to make a placement system, but I keep getting this error when using :FindPartsInRegion3withIgnoreList()

Here's the part of the script I think that is causing the problem:

	local hb = model.HitBox
	local region3 = Region3.new(
		Vector3.new(
			hb.Position.X-2,
			hb.Position.Y-3.5,
			hb.Position.Z-2.5
			),
		Vector3.new(
			hb.Position.X+2,
			hb.Position.Y+3.5,
			hb.Position.Z+2.5
			)
	)
	local partsinRegion = workspace:FindPartsInRegion3WithIgnoreList(region3, model, 100)
	local function p() 
		print(tostring(partsinRegion[1]))
	end
	pcall(p)
	-- just to test to see if it returns an object

Two problems:

• withignorelist takes a table of parts, with FindPartsInReigon3() takes a second parameter which is an instance which all its decendants should ignore.