Please make sure that your XC is powered. Remove the white cap of the XC by slightly turning it clockwise. You should then see a white RESET button. Long-press the button until you hear “system reset”. After about 30 seconds, the XC should power up again and you should hear “system startup” and “waiting for connection”. You can now set up the XC in the app again.
Please make sure that you heard “system reset” after long-pressing the reset button, and that you heard “system startup” and “waiting for connection” later. If one of these messages was not heard, please contact customer support.