First of all try doing things in this order.

1. Unplug all USB devices from the MAC including the Tappecue. 2. Shut down the Tappecue Setup program. Right click on the icon on the task bar and click close. 3. Plug the Tappecue back into USB 4. Log back on to the Tappecue app with the account you created. 5. Go to the 4th tab called utilities and click the MAC address button. Write it down. 6. Go back to the register Tappecue tab and try again to register it.   

If you are still getting an Error message it could be the drivers are not on the MAC you are using.

Use this link to download and install the correct driver for your MAC version.

After installing, reboot your MAC and try to register it again.