The network wifi adapter of windows. Inside properties/status it will tell you the mac address. Start nbahomepass then check if the mac address got changed with then one of nbahomepass. It has to be exactly the same.What do you mean by if the mac address changed inside the wifi network adapter? How do I check that?
Also I'm pretty sure your 3DS doesn't have to be connected to any wifi. So remove any wifi connection saved in the 3DS settings. It will connect to your laptop(or whatever you are using)wifi automatically since it's emulating a Nintendo zone.