Phase &, instruction &: No variable defined for characteristic &

What causes this issue?

The process instruction &V2& for phase &V1& of the process order is a
process data request. In this process instruction, the message
characteristic &V3& is assigned to the characteristic
PPPI_EXTERNAL_VALUE. This means that its value is to be assigned using
a variable. However, the variable to be used for the value assignment
is not defined in the process instruction.
No value can be assigned to the characteristic &V3&.

System Response

The data for the process instruction has been reported without the
characteristic &V3&.

How to fix this error?

INCLUDE 'NA_HA_TST' OBJECT DOKU ID TX LANGUAGE E
RESET N1
In the process order, correct the process instruction &V2& for phase
&V1&.
INCLUDE 'NA_STREZ_NEU' OBJECT DOKU ID TX LANGUAGE E
<DS:TRAN.COR2>Change process order</>
INCLUDE 'NA_HA_PROD' OBJECT DOKU ID TX LANGUAGE E
RESET N1
Errors in the process instruction cannot be corrected for the current
PI sheet.
In the message monitor, check whether the process message requested in
the process instruction was sent after you started the function for
reporting data.
<DS:TRAN.CO54>Call up message monitor</>
If the message has not yet been sent, manually add the missing value in
the monitor.
If the message has been sent but the characteristic &V3& is needed by
certain destinations, you need to manually post the data in these
destinations.
INCLUDE 'NA_PLNREZ_HINW' OBJECT DOKU ID TX LANGUAGE E
<DS:TRAN.C202>Change master recipe</>

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