My ISP has handed out IPv6 for a while, and for most of that time my home network has politely ignored it. The router got a v6 address, declared victory, and not a single device behind it could reach anything over v6. Classic.
The router itself had a global address and could ping out fine, which is the trap. It looks like IPv6 works. It does not, because the bit that matters for everyone else is prefix delegation: the ISP hands you a whole prefix (a /56 in my case) and the router is meant to carve that up and advertise sub-prefixes onto your LANs. Mine was requesting a single address for the WAN side and asking for no delegated prefix at all, so the LAN had nothing to hand out.
The fix was one checkbox and one number. Enable DHCPv6 prefix delegation on the WAN, request a /56, and assign a /64 out of it to the LAN interface with router advertisements turned on. Within seconds the laptops picked up SLAAC addresses and the global reachability test went green.
The thing nobody warns you about is that now everything has a routable address. No NAT to hide behind. That is the point of v6, but it does mean your firewall is suddenly load-bearing in a way it never quite was before, so I spent the evening making sure inbound was default-deny rather than admiring my new addresses. Worth doing properly the first time.