@Heidi Drejas (admin) , From your description, it seems five out of thirty people are failed to enroll their Apple device.
if we enroll our Apple device with "User enrollment", please check if the Apple id we used is Managed Apple id during enrollment. Research and find a detailed link describe the user enrollment. We can read it as a reference:
https://www.robinhobo.com/how-to-enroll-an-apple-device-with-ios-13-user-enrollment-mode-in-microsoft-intune/
Note: Non-Microsoft link, just for the reference.
However, if we want device enrollment, please check the "enrollment type" to see if it is set correctly.
If there's any misunderstanding or if there's anything unclear, feel free to let us know.
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