Apex domains cannot have CNAME records.
Question and response
Question
dig prod-ec1.live-agent.net. NS
Answer
prod-ec1.live-agent.net. 5 NS ns-1753.awsdns-27.co.uk.
prod-ec1.live-agent.net. 5 NS ns-847.awsdns-41.net.
prod-ec1.live-agent.net. 5 NS ns-477.awsdns-59.com.
prod-ec1.live-agent.net. 5 NS ns-1492.awsdns-58.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0