Message type: E = Error
Message class:  FOT_B2A - Messages Administration Report Electronic Data Transmission 
Message number: 815
Message text: Changes not possible when status is &1
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
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The SAP error message FOT_B2A815 with the description "Changes not possible when status is &1" typically occurs in the context of business transactions or documents that are in a specific status that does not allow for modifications. The &1 in the message will be replaced by the actual status code that is preventing the changes.
Cause: The error is caused by attempting to make changes to a document or transaction that is in a status that prohibits modifications. Common statuses that might trigger this error include: Completed: The document has been finalized and cannot be altered. Posted: The transaction has been posted to the ledger, making it immutable. Locked: The document is locked for editing due to various reasons, such as being in use by another process or user.
Solution: To resolve this error, you can consider the following steps: Check the Status: Identify the status of the document or transaction that is causing the error. You can
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