app.aventri.com has no NS records.
NS records for this zone are defined at aventri.com.
NS records for this zone are defined at aventri.com.
Question and response
Question
dig app.aventri.com. NS
Answer
The response has no answer records.
Authority
aventri.com. 900 SOA ns-175.awsdns-21.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0