If you are saying that some contacts became “blocked” immediately after updating to iOS 27, it is important to distinguish between an iOS update actually blocking contacts and a change in how contacts are being accessed or synchronized.
An iOS update does not, by itself, impose a restriction that selectively blocks individual contacts. Contact blocking is a separate iOS feature that is normally controlled by the user, and Apple provides settings for managing blocked contacts.
If the affected contacts belong to a CardDAV account, however, the situation can be different. CardDAV accounts provide contacts from a contact server and can be configured or managed by an organisation. Apple supports CardDAV accounts on iPhone and also supports configuring CardDAV accounts through device-management systems.
In a managed environment, an MDM profile or other account-level configuration can impose restrictions on access to contacts, particularly where contacts come from a managed account. Apple documents MDM controls that can prevent unmanaged apps from accessing contacts associated with managed sources and can restrict how managed and unmanaged contact data is shared.
Therefore, if only certain contacts appear to be inaccessible, unavailable to particular apps, or otherwise restricted after upgrading to iOS 27, I would not conclude that iOS 27 has blocked those contacts. Instead, check whether those contacts are coming from a CardDAV account, whether that account is managed, and whether an MDM/configuration profile is installed on the iPhone.
You can check the relevant account under Settings > Apps > Contacts > Contacts Accounts. If the account is organisation-managed, some settings may also be controlled by the administrator rather than by iOS itself.
In other words, the iOS 27 update may have exposed or coincided with a synchronization, account, or management-policy issue, but that is different from iOS 27 itself deliberately blocking individual contacts.
