What might be the cause if new iPhone devices don't enroll in MDM during deployment?

When new iPhone devices fail to enroll in Mobile Device Management (MDM) during deployment, the most likely cause is that the devices do not have an MDM server assignment. For an iPhone to enroll in MDM, it must be correctly configured to communicate with the designated MDM server. This involves assigning the devices to the MDM server during the setup process, which typically happens through Apple's Automated Device Enrollment (formerly known as DEP). If there is no assignment of the devices to an MDM server, the enrollment process cannot begin, leading to failure during deployment.

This understanding emphasizes the importance of proper device configuration and MDM setup as part of the deployment strategy. The enrollment process is designed to create a seamless provisioning experience, but it relies on the correct association with the MDM server, which must be configured ahead of time to ensure devices can connect and complete the enrollment process successfully.