Doesn't have something to do with the lockout chip? I know it wont work on front loaders with the lockout chip disabled either.
Now, here is the scary part. When we got back to my house. I immediatily ran to hook up my Top Loader and test my once in a life time find! And NO matter what I did I could not get it to work. I tried for 20 minutes. I was sweating and my bubble had burst. I realized that the seller knew it did not work and tried to sell me a crappy broken cart for $2! I was not too upset as even a broken Gold World Championship cart had to be worth hundreds of Dollars even back then when a working one was worth $5000. But, then my friend said why don't you try the front loader. A suggestion that sounded like a waste of time. But, I would have plugged it in to my atari 2600 if there was a one in a million chance it would work! So, I tore out my Front Loader and dusted it off. Plugged it in and the rest is history!
Sorry for the long winded story. But, It is my greatest finds ever. And all for $2!
Same thing happened to me. The NWC won't work in a top loader.