Output & for medium &, partner function & is not defined

What causes this issue?

You have selected a combination of output and partner function which
has not been defined.

How to fix this error?

INCLUDE NA_EINGABE_PRUEFEN
This is a warning message. You can proceed by pressing ENTER.
To prevent the warning message from appearing again, assign the
required partner function to your output type in table TNAPN.
IF &DEVICE& = 'SCREEN'
<DS:TRAN.NACT>Execute function</>
ENDIF

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