Don't press down -- that clears all of trip data.
You have to slide it out without any downward pressure. Not hard to do, once you get the hang of it.
The Strada computers don't have a button on the surface. It is on the back side, and the entire computer is hinged in the mount. This means that pressing down on the face pushes the button on the back (a clever design that is hard to explain in type).
When you push down, you are, in effect, clicking the button to go from time, max speed, average speed, etc., and if you push down for longer than a moment, you are telling the Strada to clear the data decks.