Message type: E = Error
Message class:  UPP_LB - Layout Builder: Messages 
Message number: 023
Message text: Call up the last screen of the Layout Builder
Changes were made to the layout. These changes affect the appearance of
the layout on the screen. The last screen of the Layout Builder has not
been called up since the changes were made. Therefore, the changes have
not become effective in the display. The status of the layout is now
inconsistent.
If you exit the Layout Builder, the data will be lost.
Complete the layout by calling up the last screen of the Layout
Builder. This way, your changes will be automatically included in the
layout.
The system issues an error message and will not allow you to continue with this transaction until the error is resolved.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message UPP_LB023, which states "Call up the last screen of the Layout Builder," typically occurs in the context of the SAP User Experience (UX) and specifically when working with the Layout Builder in SAP Fiori or SAP UI5 applications. This error can arise due to various reasons, including issues with the layout configuration, missing components, or problems with the underlying data model. Causes:
Configuration Issues: The layout may not be properly configured, leading to an inability to render the last screen. Missing Components: Required components or libraries may not be loaded or available in the system. Data Model Problems: The data model that the layout relies on may be incomplete or incorrectly defined. Authorization Issues: The user may not have the necessary authorizations to access certain components or data. Technical Errors: There may be underlying technical issues, such as bugs in the application or problems with the SAP system itself. Solutions: Check Configuration: Review the
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