Path.Status says Enum.PathStatus.NoPath why?

local pathfindingService = game:GetService("PathfindingService")
local pointModel = Instance.new("Model")
pointModel.Name = "Points"
pointModel.Parent = game.Workspace

function visualizePath(path)
    -- clear old path visualization
    pointModel:ClearAllChildren()

    -- calculate new visualization  
    local points = path:GetPointCoordinates()
    for _, point in ipairs(points) do
        local part = Instance.new("Part")
        part.FormFactor = Enum.FormFactor.Custom
        part.Size = Vector3.new(1,1,1)
        part.Position = point
        part.Anchored = true
        part.CanCollide = false
        part.Parent = pointModel
    end
end

function GetPath ()
    local start = game.Workspace.Start.Position
    local target = game.Workspace.End.Position
    local path = pathfindingService:ComputeRawPathAsync(start, target, 500)

    visualizePath(path)
    -- Check to see if the path was computed correctly
    print (path.Status)
    if path.Status == Enum.PathStatus.FailStartNotEmpty or path.Status == Enum.PathStatus.FailFinishNotEmpty then
        print("Compute failed")
        return {}
    end

    return path:GetPointCoordinates()       
end

wait ()
while true do
    wait (9)
    GetPath()
end