AT&T Uverse gateway hookup?

So a couple days ago my uncle moved out and took the desktop computer with him, leaving just our gateway. He accidentally took the power cord that it came with but I realized that my ASUS laptop plug fits in. When powering it up, the broadband link is a flashing red with no light all on the "service". I spent 40 minutes on the phone with at&t and they did line tests and came to the conclusion that the gateway is bad. I find this hard to believe as it is pretty coincidental that it goes out right after we remove the computer (which the att rep said the gateway doesn't need a computer). Is it possible I need the real power cord or am I doing something else wrong, the phone line is hooked up and also the cable line. What else is there?