Calix Gigacenter routers on the latest firmware block ARP-spoofing by default, which is a critical part of Circle's method of web filtering. Significant issues may occur on your Gigacenter's network when you have Circle paired, including not being able to connect to the internet on any filtering level other than None.
To allow this router to work with Circle, ARP-spoofing must be Enabled in the Security section of the router's control panel.
Login to your router settings (see Calix's instructions if you need assistance) then head to Security > ARP Spoofing, you can enable/disable ARP Spoofing. Enable ARP Spoofing when using Circle or other network monitoring hardware on your network. ARP Spoofing allows the Circle device to monitor all traffic on the home network automatically and without special configuration.