Final answer:
The MDM enrollment process for a new, customized Android device likely fails because the device is rooted. Rooting raises security concerns, which leads many corporate MDM policies to restrict such devices from accessing corporate resources.
Step-by-step explanation:
The most likely reason the MDM (Mobile Device Management) is not allowing enrollment of a highly customized Android device could be that the device is rooted. Rooting is a process that gives users privileged control over the subsystems of Android, which can raise security concerns for corporate resources. Most corporate MDM policies restrict the enrollment of rooted devices because they bypass the security protocols that ensure the safety of corporate data.
Other potential reasons such as the OS version not being compatible, the OEM being prohibited, or the device not supporting FDE (Full Disk Encryption) would typically be known before the enrollment process, especially if the device is new and fully updated. Therefore, rooting stands out as the most probable cause as it can be done post-update and may not be immediately apparent to the systems administrator or MDM software.