Hello.
I wish confirm what all test should work via IPv6.
Block pinging your addresses is a bad idea at all, especially during testing (If you do this, sure).
Look at your domain ping:
user@Ubuntu-Desktop:~$ ping anirbansengupta.co
PING anirbansengupta.co(2405:201:6408:2fd4:9cea:65b7:1e1b:abc5 (2405:201:6408:2fd4:9cea:65b7:1e1b:abc5)) 56 data bytes
^C
--- anirbansengupta.co ping statistics ---
73 packets transmitted, 0 received, 100% packet loss, time 73729ms
user@Ubuntu-Desktop:~$ ping -4 anirbansengupta.co
PING anirbansengupta.co (148.66.138.140) 56(84) bytes of data.
64 bytes from 148.66.138.140 (148.66.138.140): icmp_seq=1 ttl=41 time=203 ms
64 bytes from 148.66.138.140 (148.66.138.140): icmp_seq=2 ttl=41 time=203 ms
64 bytes from 148.66.138.140 (148.66.138.140): icmp_seq=3 ttl=41 time=203 ms
64 bytes from 148.66.138.140 (148.66.138.140): icmp_seq=4 ttl=41 time=203 ms
^C
--- anirbansengupta.co ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 203.277/203.379/203.446/0.064 ms
When I connecting to your domain via web browser I receive:
Forbidden
You don't have permission to access this resource.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.
And this possible only via IPv4, since via IPv6 it's not accessible!
I wish recommend you to use 3-rd domain level for this kind purposes, for example ipv6.anirbansengupta.co.
And look to your web server, in case of access rights and available files (not only *.html).