Unless its been modified, the standard door, you need to pull it out towards you (keeping it level) and once out all the way, then down. It should shut then. Its a very awkward mechanism. It will give some resistance as when its closed and you press the button, it retracts on its own. I believe there was an aftermarket door you could get that was driven off a small motor, but I dont know how those ones work.
If you could post a pic that would be great as there are a couple of versions.