Apple Business Manager - Manual iPhone Enrollment Failing with Error 0x80EF

Hello:

I am trying to migrate my company's devices to our new Apple Business Manager subscription. So far, we have been successfully migrating MacBooks, but today attempted our first iPhone manual enrollment.

We have been trying to follow the steps here: Add devices from Apple Configurator to Apple Business Manager - Apple Support

Unfortunately, the device enrollment preparation fails on the final step with the following error message:

"Provisional Enrollment failed. [MCCloudConfigErrorDomain – 0x80EF (33007)]"

I have confirmed the device is not tied to activation lock, and is on the most current version of iOS available.

I also noticed that my enrollment profile (which is ONLY WiFi as recommended in other places) installs correctly, as the iPhone connects to the WiFi network.

Additionally, when I subsequently proceed through the setup on the iPhone, it does detect it has a remote management enrollment profile, but the enrollment retrieval fails with message "cancelled".

I should note that the device has never appeared in my device list in the portal at https://business.apple.com

There are lots of articles about this error online, but seem to be regarding issues with third-party MDM systems like Jamf. Can anyone provide help for Apple Business Manager iPhone manual enrollment?