Got mine working last night. Apparently the documentation is lacking some details and should include the section below.
by default, IPV6 is disabled on Raspbian or the OS that OSPi uses.
see here: https://www.raspberrypi.org/forums/viewtopic.php?t=15886
The documentation should include this critical step (or maybe the update script should do it automatically):
Add IPV6 module to your OS by doing this: “sudo nano /etc/modules”, add “ipv6” at the end, reboot.
Restart OpenSprinkler (if it’s not started automatically): sudo /etc/init.d/OpenSprinkler.sh restart
That’s it.