After deploying new VMs, the systems administrator notices it is not possible to connect to them using network credentials; however, local accounts work. After logging in, the administrator notices…

This restates a dependency rather than identifying a cause - it describes what directory services needs rather than naming the resulting failure condition of time being out of sync.

Licensing issues would not selectively block network credential authentication while allowing local account logins to succeed simultaneously.

A directory services outage would prevent all domain authentication from reaching controllers, but the specific clue of missing NTP servers points to a time synchronization failure rather than a service-level outage.

Kerberos, the authentication protocol underlying Active Directory network logins, enforces a maximum clock skew of 5 minutes between a client and the domain controller. New VMs without NTP configured have no authoritative time reference and will drift past this threshold, causing Kerberos ticket validation to fail - which blocks network credential logins while local accounts, which do not rely on Kerberos, continue to work.