On some devices which have only Wi-Fi connection the default generated MAC address could be 00:1A:79:00:00:00 which means the app couldn't properly detect it because of Android restrictions. If you have such an issue just change the 00:00:00 part to any random hexadecimal digits.
Note: If you get the MAC address not found when trying to activate, try exiting the STB emulator, remove it and reinstall, when you re-enter the MAC here exit the STB emulator and re-enter.
The STB emulator can be a bit finicky so if you get any errors try exiting and rebooting, or uninstalling the app and reinstalling, as you can see from the screenshots it definitely works and should do for you with some patience. 2b1af7f3a8