I suspect you burned that strip out.
Another idea is to get three of the strips and wire them in series. Then you would have 4 volts on each which is probably enough. DO NOT wire them in parallel, or you'll burn out all three. Series is one wire from the first one wired to a wire on the second one, then the second wire from the second one to a wire on the third. Minus to plus, minus to plus. Then the two free wires to the 12 volts. So the whole thing is a single loop. If you're not sure about this, I'd suggest doing a little more research.
Tom