Explanation
A corporate security policy can restrict a corporate-managed mobile device from updating its OS automatically, even if the auto-update feature is turned on. This can be done to prevent compatibility issues, security risks or performance problems caused by untested or unwanted updates. The device administrator can control when and how the updates are applied to the device. The device not having enough free space, needing domain administrator confirmation or being incompatible with the newest version of the OS are not likely causes of the issue, since the user would receive an error message or a notification in those cases. Verified References: https://www.comptia.org/blog/mobile-device-management
https://www.comptia.org/certifications/a