I've tried just about everything - battery won't charge

Okay so I'm trying to fix my girlfriends Gateway M-series laptop. There is a power issue. For some reason the computer wont charge the battery. I don't know what it says when its on because it wont charge to keep the computer on. I'm not sure if this computer has any other problems, but the power adapter is new, and the battery is new as well. I thought there might be a problem with the power jack on the motherboard and had one of the local tech guys in the area replace it with a new one. The battery I had just put in last night and charged it, and the instructions said to let it run all the way down and then recharge it as with normal batteries. So I did that and it shut off cuz the battery went dead and now it wont charge back up. The purple light is blinking on it, not solid like it should be when it is charging. Does anyone have any clue what this is because no one around here seems to have any clue and gateway are a bunch of shysters that wont talk to you for support.