IP6Tables config not saving

Hi there.
I have just switched FirewallD to IPTables on a brand new clean CentOS 7 with just VirtualMin installed.

I’ve accessed the Linux IPv6 Firewall menu option, pressed ‘Reset Firewall’ and then ticked the bottom option (Block all except ports used for virtual hosting, on interface), and then pressed Setup Firewall, but nothing happens. The Setup Firewall button greys out, but it never does anything else.

I did the same thing for the Linux Firewall IPv4, and this went through correctly and saved the config, but not for IPv6 for some reason. Can anybody help?