I'm trying to linearly unwrap a wheel into 4 lines. So I select the 1st 1/4 faces, U->Follow Active Quads, and the unwrap shows up in the UV editor. Then I select the next 1/4 of faces, U->Follow Active Quads... nothing happens. Try another set of faces. Same thing.
Why can I unwrap any more faces?
None of the suggested answers helped. The point of this question is that nothing happens when I hit unwrap. Nothing shows up in the UV editor.