How to get this line show up in FreeStyle

Hi I try to find out a way to render the cross line in FreeStyle. But currently the FreeStyle could not get the cross objects’ line show up. Is this a functional issue or my set up incorrect?

The below two object have a cross face.

Once I click the render, I will get below effect. The line just gone!

And if I enable the face, I will get a result like this, which I don’t like it yet.

Hope anyone could share some idea. Thanks!

Is it a static object or do you need to animate one of the cubes? If you’re not going to have them move around separately you can apply a boolean union modifier to them and mark the edges of the resulting mesh manually.

Bear in mind this is only optimal for cubes. More complex shapes would require the union as a guide object and a lot of time pushing vertices with edge/face snap enabled.

Freestyle can’t do lines for object intersections.
If static I would add edge loops and mark the edges as freestyle edges. If animated use an object ID on one object and in the compositor apply a sobel filter to that object ID creating your own edges. Use a colour ramp to crush any artifacts.