Firewalla by default (as of 6/29) does not automatically support ipv6 in Simple mode. It is likely in the near future, we will automate this after we have tested this across the world. (Even the IPv6 standard is old, IPv6 Deployment is fairly slow ... and new ... and different across service providers)
This only applies if you are in Simple mode.
Tap on the + sign, this will add an ipv6 feature
Tap on IPv6 Feature
Tap on button