In this case, it’s because your DNS service is not working correctly.
$ dig +dnssec +norecurse @dns2.registrar-servers.com test.nexoya.io
; <<>> DiG 9.15.7-Ubuntu <<>> +dnssec +norecurse @dns2.registrar-servers.com test.nexoya.io
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 41617
;; flags: qr aa; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;test.nexoya.io. IN A
;; AUTHORITY SECTION:
nexoya.io. 3601 IN SOA dns1.registrar-servers.com. hostmaster.registrar-servers.com. 1577071590 3600 1801 604800 3601
nexoya.io. 3601 IN RRSIG SOA 13 2 3601 20200102000000 20191212000000 15848 nexoya.io. FOVEHT6JV+iw3OECbwr1P0b9PxX9UrmBSU+RXQPmOMqq65U/nJKVQ3uu iugbk2rVRPmuk6dph1uze+apMjAuIw==
;; Query time: 0 msec
;; SERVER: 2610:a1:1025::200#53(2610:a1:1025::200)
;; WHEN: Fri Dec 27 09:42:43 UTC 2019
;; MSG SIZE rcvd: 221
Because the zone uses DNSSEC, the response has to include some additional records proving that the name and type at issue don’t exist. It does not.
You might be able to work around the bug by creating some kind of DNS records named
test.nexoya.io. It could be
CAA records (which would have to be correct, of course), or an
A record, or a
TXT record with a sad face emoticon. Just something. That might inspire the DNS service to behave correctly.
Namecheap outsources their DNS servers to a company called Neustar. Intriguingly, this same issue was reported recently regarding another Neustar customer, PayPal.
paypal.com uses two different DNS services – Neustar and a competitor – and the other one works correctly.)
It seems likely that there’s some kind of bug in Neustar’s platform.
…It goes without saying that you could also switch to a different DNS service, or ask Namecheap to fix it.
Turning off DNSSEC, if you can do so, would also avoid the issue.