IPv6 addresses not accessible over internet.

[cclloyd]

I have an experimental gitlab server accessible only on IPv6 (I set the listen address to "[::]")

I can access it over IPv6 fine, but only on my home network.  If I try to access it over the internet (say from my phone over LTE [confirmed LTE had ipv6 by going to ipv6.google.com]), the connection times out. 

My WAN interface is using DHCPv6, and the server is confirmed to have IPv6 connectivity.

Why can't I access it using ipv6 over internet?