Hi,
Since October 2017, a majority of directory authorities check relay IPv6 ORPorts.
If your relay is configured with an IPv6 ORPort:
ORPort [IPv6]:Port
and it is not reachable over IPv6, it will be excluded from the consensus. This can happen if the address is wrong, or the IPv6 routing is wrong.
If your relay isn't in the consensus, it will log warnings.
Or, you can check Relay Search at: https://atlas.torproject.org
If your relay is not Running, you can check the votes for your relay here: https://consensus-health.torproject.org/consensus-health.html
If all the authorities don't vote for your relay, it has a tor or IPv4 problem. If a few do vote Running, it probably has an IPv6 problem. (If you want to be sure, check which authorities support ReachableIPv6 in the consensus health Known Flags table.)
If you have an IPv6 problem, check the address, and check the routing.
Here's what I do to check IPv6 on my relays when I set them up:
From the relay: ping6 ipv6.google.com
From another IPv6 machine: ping6 ipv6.google.com ping6 (the relay's IPv6 address) telnet (the relay's IPv6 ORPort)
We're working on having better support for IPv6 across Relay Search and consensus health.
T