How To Fix 55021 - Function &1 unknown

55021 - Overview

• Message type: E = Error

• Message class: 55 - Messages for development class EENO

• Message number: 021

• Message text: Function &1 unknown

What causes this issue?

You have called a function that the transaction/system does not know.
Either the function has not been implemented, even though there is a
menu option or a pushbutton, or an incorrect function code has been
transferred to the program (error in SAPGUI).

System Response

The system cannot execute this function.

How to fix this error?

Make a note of the function code (&V1&) stated in the error message and
of the status of the screen (via System->Status) and send a problem
message to SAP.

Error message extract from SAP system. Copyright SAP SE.

55021 - Details

• The SAP error message "55021 Function &1 unknown" typically indicates that the system is trying to call a function module or method that does not exist or is not recognized by the system. This can occur for several reasons, including:
  Causes:
  
  Typographical Error: There may be a typo in the function name being called.
  Function Module Not Created: The function module may not have been created or activated in the system.
  Authorization Issues: The user may not have the necessary authorizations to access the function module.
  Transport Issues: If the function module was recently transported from another system, it may not have been imported correctly.
  Namespace Issues: The function might be in a different namespace that is not accessible in the current context.
  Version Mismatch: The function module may exist in a different version of the software or in a different client.
  
  Solutions:
  
  Check for Typos: Verify that the function name is spelled correctly in the code.
  Function Module Existence: