Nameservers select the DNS authority
At the registrar, a domain's nameserver setting delegates DNS authority to a provider. After that delegation is active, record edits must be made at the provider that answers authoritatively, not at an old DNS dashboard that is no longer in use.
A nameserver change can affect every service whose records live in the zone, including websites, mail, verification tokens, and subdomains. Before switching, inventory the records and recreate the needed set at the destination provider.
Records define individual services
Within the active zone, records such as A, AAAA, CNAME, MX, and TXT direct particular names or describe service policies. Changing one record generally targets that name and purpose, while the zone remains under the same authority.
Confirm the currently delegated nameservers before editing and verify the authoritative answer after the change. Avoid changing delegation and several records at once without a plan; separating the steps makes it easier to identify which layer caused an outage.