Website not opening or shows default page after Plesk upgrade/migration.
DNS records are different from Plesk DNS and from 3rd party DNS servers:
nslookup domain.tld 127.0.0.1 Server: localhost Address: 127.0.0.1 Name: domain.tld Address: 203.0.113.2
nslookup domain.tld 18.104.22.168 Server: google-public-dns-a.google.com Address: 22.214.171.124 Non-authoritative answer: Name: domain.tld Address: 126.96.36.199
DNS propagation is in progress or authoritative DNS server is misconfigured.
Make sure you have correct DNS server specified on registrar side. If everything is fine then you need wait up to 48 hours for DNS zone propagation.