macbook air won't charge

I have a 11" macbook air that's about two years old, and a week ago it just stopped charging. When I plug in the charger (MagSafe 2), there's no light and no indication that the battery is charging. I've tried my charger in every outlet in my apartment and at the cafe across the street, and nothing. I've tried it with and without the extension cord, nothing. I've reset the SMC about a dozen times, sat on my charger, warmed it up with a hairdryer, and I even have a MagSafe to MagSafe 2 converter so I can try my original MagSafe charger, and nothing. In fact, the only place that it will charge is at the genius bar at the Apple store. I've been twice, and every time they plug it in (either with my charger or theirs) it charges just fine. I even got a new charger, and still nothing. I've ordered an external battery to see if it will charge that way, but I'm worried it still won't work. My husband's macbook charges just fine in the apartment, so I have a hard time believing that it's my apartment that's the problem. I have no idea what to do and neither does anyone from Apple that I've talked to. Has anyone had any luck with external batteries? Do I just have an expensive paperweight now?