As of iOS7, software access to your device’s MAC address is restricted.
In order to view the local MAC address in IP Scanner Mobile it is now necessary to consult the General->About->Wi-Fi Address in the Settings app, and then copy/paste the address manually into the field labelled ‘Local MAC address’ in the IP Scanner prefs.
N.B. This pref is NOT in IP Scanner itself, but in the general Settings app on your iOS device home screen.
As soon as we have found a way to obtain the MAC address without this manual step, rest assured that we will integrate it ASAP but for the moment this is where we are. 🙁