Message type: E = Error
Message class:  ICC_FI_CN - Für die Meldungen extern vornum. Belege 
Message number: 006
Message text: Reference invoice &2 blocked by user &1
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The SAP error message ICC_FI_CN006, which states "Reference invoice &2 blocked by user &1," typically occurs in the context of financial transactions, particularly when dealing with invoices in the SAP system. This error indicates that a specific invoice (identified by &2) is currently blocked for processing by a user (identified by &1).
Cause: User Lock: The invoice is locked by a user who is currently editing or processing it. This could be due to a transaction that is still open or has not been completed. Authorization Issues: The user attempting to access or process the invoice may not have the necessary permissions or authorizations to do so. System Configuration: There may be specific configurations or settings in the SAP system that enforce blocking of invoices under certain conditions.
Solution: Identify the Locking User: Check who is currently locking the invoice. This can often be done through transaction codes like SM12 (to view locks) or SM21
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