gtm-co2.serverdata.net has no CNAME records.
Question and response
Question
dig gtm-co2.serverdata.net. NS
Answer
The response has no answer records.
Authority
serverdata.net. 2439 SOA ns2.serverdata.net. hostmaster.serverdata.net. 2026022408 3600 1800 1814400 3601
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0