I made a thread on the Neo Geo forums, after much troubleshooting we were not able to solve the problem. I even got a replacement card and still no luck. My console reads official SNK memory cards fine, I even opened up the console and inspected the board- it looked perfectly fine with all the traces still in good shape and nothing wrong around the memory card slot.
The conclusion we came to is that this card may simply not work on later models of the AES system. I'm going to wait for the NeoSaveMasta to go back in stock.