Why isn’t my headphone-jack card reader working on iOS?

When you update your device to iOS 7, our app will ask your permission to access the microphone on your mobile device. In iOS 7, this must be enabled in order to use a headphone-jack card reader. To confirm you have granted the app permission to access the microphone, follow this quick path:

Settings > Privacy > Microphone > Turn on CC Terminal (success indicated by a green bar.)

Once this is confirmed, launch the app and plug in the card reader to swipe.