I recently got a new phone and set up my coin app and cards on the new device. I followed all the instructions on the coin website, but was unable to get my card to sync with the new phone even after resetting the coin.
I would hit sync on my phone, and then hold the button on coin to put it in sync mode, but coin would just turn off after a few seconds.
Problem: This happens if you set up your new coin app with the same tap-code as you used previously.
Resolution: Change your tap code on your new phone, then you will be able to sync the coin. After syncing you can change your tap code back to what you used before.
Hope this helps others!