I followed https://www.digitalocean.com/community/tutorials/how-to-enable-ipv6-for-digitalocean-droplets to enable and configure my droplet. I can ping6 myself but when it comes to the gateway or other ipv6 addresses, it returned "Destination unreachable: Address unreachable". I checked the routing table, the firewall and the network interfaces configuration and found no errors. I created another new droplet which works well, and the configurations I mentioned above in the new droplet looks all the same with my old one. I find this weird. Could this be a digitalocean problem rather than my own?