Short answer Clear stale client DNS data, query the record again and confirm which resolver answered.
When to use it
After a DNS change or when browsers and nslookup return different results.
Clear client cache
ipconfig /flushdns
ipconfig /registerdnsNote
The second command requests domain DNS registration.
Query a specific resolver
Resolve-DnsName example.com -Type A
nslookup example.com <DNS_SERVER_IP>Note
Compare the returned address with the expected IP.
Caution
A server-side DNS problem cannot be fixed by clearing only the client cache.