Why are my contacts and/or leads in Salesforce not synced to Zendesk when they're created?
If the Ongoing Sync is enabled, but the integration is not adding users in Zendesk when Contacts and Leads are created in Salesforce, verify how the Contacts and Leads are created. By default, the Ongoing sync cannot sync any profile created from a Bulk, Batch, or Future job run by a 3rd party Salesforce integration (such as MailChimp).
If Contacts and Leads are not synced on creation or update, please ensure that the Ongoing sync is enabled.
To verify, visit the Zendesk tab in your Zendesk for Salesforce integration and select Go to Mappings under User and Organization Sync Settings:
Once in the User and Organization Sync Settings, verify that Enable Updates is set to Yes: