Symptoms

The following error occurs when trying to save a domain in RCP:

An error has occurred, please read the message below:
Nameserver creation or update failed: 
n1.nameserver.tld, 2305, Object association prohibits operation 

Cause

 Nameserver ns.nameserver.tld doesn't exist in the DNS service.

No data about nameserver.tld is retrieved from WHOIS output nor there is an answer when querying its A record via a DNS lookup utility.

dig n1.nameserver.tld 

; <<>> DiG 9.9.4-RedHat-9.9.4-38.el7_3.3 <<>> n1.nameserver.tld
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 47410
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

Resolution

Make sure third-party nameservers that you are trying to assign to a domain actually exist and resolve publicly.