Apex domains cannot have CNAME records.
Question and response
Question
dig greenharborsoftware.com. NS
Answer
greenharborsoftware.com. 5 NS ns2.greenharborsoftware.com.
greenharborsoftware.com. 5 NS ns1.greenharborsoftware.com.
Authority
The response has no authority records.
Additional
ns1.greenharborsoftware.com. 5 A 45.59.107.74
ns2.greenharborsoftware.com. 5 A 209.212.157.223
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0