Noticed this the other day after a high speed run, while I couldn't actually visually see if the spoiler was up, (I am not going to try to stand up and look at the back of my car at 100mph), I did not have a dash light indicating that the spoiler was up. When I got home I manually raised the spoiler and it functioned fine, light on dash came on as designed.
So, what would prevent the spoiler from operating while driving?