ATO (Adaptation Transport Organizer) configuration is mandatory for creating/editing FLP spaces/pages since S/4HANA Cloud 2102.
If you try to create or edit a space/page in a system without ATO, you get the error message: Space XXX is in customer namespace and requires ATO transport handling.
S/4HANA Cloud 2102 or higher version
We have implemented a more restrictive check that enforces ATO for spaces/pages to avoid inconsistent objects – this will become active for S/4 HANA Cloud 2102.
Please set up ATO on your S/4HANA Cloud system.
More details please refer to note 2283716 - Key User Application is not configured.
Manage Launchpad Spaces, Manage Launchpad Pages, Extensibility Settings , KBA , CA-FLP-ABA-DT , SAP Fiori Launchpad ABAP Content Admin Tools , Problem