ns2.throughputclimb.com has no AAAA records.
Question and response
Question
dig ns2.throughputclimb.com. AAAA
Answer
ns2.throughputclimb.com. 4 CNAME throughputclimb.com.
Authority
throughputclimb.com. 3138 SOA dns.throughputclimb.com. hostmaster.throughputclimb.com. 1685522137 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0