Hello,
I tried reaching mega.co.nz using your tunneling service. While online-ping-services show that there's ipv6-connectivity to mega.co.nz, I cannot get this done through your tunnel (and I tried different ones from the looking glass). Also, not only pinging is the issue, but also visiting the site.
Now I do not know if this is a routing issue, or if mega.co.nz blocks all requests on IPv6 from your endpoints.
Their hosting is single-homed behind Cogent, which lacks routes to the HE network.