Message type: E = Error
Message class:  FKK_ID_PT_SIGN - Digital Signature Portugal FI-CA/IS 
Message number: 504
Message text: Invalid length in 'From Number'. Specified value must have length &1
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The SAP error message FKK_ID_PT_SIGN504 indicates that there is an issue with the length of a number that has been specified in a transaction or configuration related to the contract accounts receivable and payable (FI-CA) module. The error message typically states that the specified value must have a certain length, which is indicated by the placeholder &1.
Cause: The error is usually caused by one of the following reasons: Incorrect Input Length: The value entered for a field (likely a number or identifier) does not match the expected length defined in the system. For example, if the system expects a 10-digit number and you provide a 5-digit number, this error will occur.
Configuration Issues: There may be a configuration setting in the system that defines the expected length for certain fields, and this setting may not align with the data being processed. Data Migration Issues: If data has been migrated from another system, it may
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