You can sign-in to the iPhone TapeTrack app using either a 4 digit Passcode, or your iPhone's Touch-ID sensor (if supported).

In the event you have forgotten your Passcode, you can reset the pin using the Reset PIN button on the Sign-in Settings screen. If you select this option your adapter settings (including credentials) will be erased. Please note that as the adapter data is hosted remotely this will not be erased.