GDPR consent field is outputing as an empty div on the user registration form

This can't be a bug or other people would be reporting it. But does anyone have any thoughts on what might be happening?

A consent form is created, and a field referencing it added to the user account fields. It is showing when creating a new user as an admin. When registering one's own account, as an anonymous user, it however displays no text, field, or checkbox and gives an error when submitting the form. Inspection of the HTML reveals this empty, if class and ID heavy, div:

<div class="field--type-gdpr-user-consent field--name-field-consent field--widget-gdpr-consent-widget js-form-wrapper form-wrapper" data-drupal-selector="edit-field-consent-wrapper" id="edit-field-consent-wrapper"></div>

And the error when submitting:

This value should not be null.

All the templates are from Drupal core's 'stable' theme directly; no overrides on the user registration form or for any form elements.

I've enabled any potentially related GDPR permissions, and confirmed there's no field permissions module installed.

I've triple-checked that the GDPR Consent field is in the displayed section of Manage Form Display and Manage Display of user accounts, and there are no custom display settings.

And, of course, i've cleared caches 150 times.

Any ideas?