Using activities in Entity Reference field - activity not found.

Problem/Motivation

Creating a content type in Drupal 10 that includes an entity reference to activities. These happen to be case activities.

Selecting the relevant Activity Type bundle.

Populating the field with the activity ID using Entity Prepopulate.

When saving the node get the error message "There are no civicrm activity entities matching [activityID]

Other CiviCRM entity reference fields for Contact and Case are working OK on the same form.

Steps to reproduce

Create a content type with an activity entity reference. Populate the entity reference field and save.