In some cases the easiest solution to a problem is to just start over. Do so on Android with these steps:
Un-pair the pin.
Turn the pin on and then hold the button on the pin for 5s (until the pin displays a message saying "Pairing: add the pin in your app").
Remove the pin in the app.
Go to the "MY PINS" tab in the app. Then press the pin for a couple of seconds until the app asks you if you're sure you want to delete the pin and answer "Yes". If the list is empty no action is needed.
Manually remove the pin from the phone.
Go to your bluetooth settings (settings > connected devices > bluetooth, may be different on some devices). Select the pin in the list of Paired devices (if it appears there) and click "Forget".
Turn Bluetooth on and off.
To make sure the Bluetooths cache is empty turn your bluetooth radio off and then on again. (To can do this in the same place as in step 3).
Restart phone (for some devices).
Some users have reported that the bluetooth Cache is not reset until the phone is restarted. If step 1-4 does not work, try restarting the phone as a final step.
Good work! Now the pin and the phone are unpaired from each other. Restart the app and try connecting again.