You need the QR code to pair the Signal with Sonic, and you should be able to find a QR code or a serial number printed underneath the shut-off valve handle of the Sonic itself or at the back of the installation code.
Also, If you experience any issues connecting your Signal to a Bluetooth, please make sure that you have the latest operating system update on your Android or Apple mobile devices.
If you have any questions, feel free to chat with us or email us at support@hero-labs.com.