Message type: E = Error
Message class:  CNVA_20400_CHECK - Messages for contorlling areas checks 
Message number: 051
Message text: There are automatic account assignments in cost element (order posting)
Error message extract from SAP system. Copyright SAP SE.
The SAP error message CNVA_20400_CHECK051 indicates that there are automatic account assignments in the cost element during an order posting. This typically occurs when you are trying to post costs to an order, but the system detects that the cost element involved has automatic account assignments that are not compatible with the posting.
Cause: Automatic Account Assignment: The cost element you are trying to use has been configured with automatic account assignments that do not match the type of posting you are attempting to make. Cost Element Configuration: The cost element may be set up incorrectly in the system, leading to conflicts during the posting process. Order Type Restrictions: The order type you are using may have specific restrictions or configurations that do not allow certain cost elements to be posted.
Solution: Check Cost Element Configuration: Go to the transaction code KA03 (Display Cost Element) and check the configuration of the cost element in question. Ensure that the
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