3391407 - Error "Object YY1_xxx can't be associated, it requires at least one root key field." – SAP S/4HANA Cloud

Error "Object xxx can't be associated, it requires at least one root key field." occurred, when publishing a custom business object.

SAP S/4HANA Cloud 

1. Creating a custom business object in app Custom Business Objects.

2. Activating the checkbox "Can Be Associated".

3. Publishing the custom business object.

4. Error message "Object xxx can't be associated, it requires at least one root key field." shows up. 

To enable one custom business object to be associated by another custom business object for reference and for use as value help, it's necessary to define one or several keys in the root node of the custom business object. If a custom business object is marked as Can Be Associated, the key fields can't be of type Association to Business Object.

Activate the checkbox Key in the field that you want to base the association on.

For more information, please check the following documentations:

• SAP Help Portal - Enabling Associations

Can Be Associated, Custom Business Object, Object xxx can't be associated , KBA , BC-SRV-APS-EXT-BO , Custom Tables and Nodes , Problem