Finally.

I went down this morning and played the only slightly bitchy American and explained that yes, I had tried swiping my keycard many different ways and no, my door still wouldn't lock and that I needed it to by 4:30 today. The lady was actually understanding and listened this time, and they came and fixed it while I was in class. My door locks, and now I'm on my way to register before we take off for homestay.
Love to all!