Apex domains cannot have CNAME records.
Question and response
Question
dig ispsystem.net. NS
Answer
ispsystem.net. 5 NS ns2.ispsystem.net.
ispsystem.net. 5 NS ns1.ispsystem.net.
Authority
The response has no authority records.
Additional
ns1.ispsystem.net. 5 A 62.109.13.129
ns2.ispsystem.net. 5 A 94.130.173.174
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0