You can manually check your DNS operation. Try this command (works on Windows and Linux):
nslookup google.com
If your DNS works for IPv6, you should get both IPv4 and IPv6 addresses in the reply. This is what I get using Ubuntu on my DNS server PC:
Server: 127.0.0.53
Address: 127.0.0.53#53
Non-authoritative answer:
Name: google.com
Address: 142.251.222.238
Name: google.com
Address: 2404:6800:4006:806::200e
And from Windows:
Server: lith.6.jsw.gen.nz
Address: 2406:e001:1:2802::12
Non-authoritative answer:
Name: google.com
Addresses: 2404:6800:4006:810::200e
142.251.222.238
If you do not get IPv6 addresses in the reply, then there is a problem with your DNS.
