Apex domains cannot have CNAME records.
Question and response
Question
dig ispsystem.com. NS
Answer
ispsystem.com. 5 NS ns-865.awsdns-44.net.
ispsystem.com. 5 NS ns-1960.awsdns-53.co.uk.
ispsystem.com. 5 NS ns-245.awsdns-30.com.
ispsystem.com. 5 NS ns-1403.awsdns-47.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0