The .IT registry have unique requirements in regards to nameserver compliance; Updating nameservers therefore requires certain parameters to be adhered to.
The specified nameserver must be the same as the one indicated within the SOA record of the domain name.
For more on glue records, please see the How to use your domain as a nameserver guide.
There must be at least one A record or MX record for the domain, and neither must be associated with a CNAME.
The names of the authoritative nameserver for the domain name but not be CNAMEs, and must respond authoritatively when queried by the IT registry.
For ease, the information generated with dns-check.nic.it should be given to the prospective nameservers that are attempting to be used.
Simply place the domain in question within the '.IT DOMAIN NAME' box, and add the relevant nameservers below. Finally press the 'DNS Configuration Check' to view if all requirements are passed.