You are getting the error because the installation of the package was not properly done.

First, you need to install the types.sql and then reinstall the package and its body. Below is the location of the types.sql:

https://github.com/mortenbra/alexandria-plsql-utils/tree/master/setup

You may also need to install other scripts in the setup directory.

Try to match download part as below:

DECLARE
    L_BLOB           BLOB;
    L_LENGTH         INTEGER;
BEGIN

    -- create new temporary BLOB
    DBMS_LOB.CREATETEMPORARY(L_BLOB, FALSE);
    
    --get bLOB
Lob_loc := bfilename('ABC_DIRECTORY','data file.zip');
OWA_UTIL.MIME_HEADER( 'application/zip', FALSE );
    
    -- determine length for header
    L_LENGTH := DBMS_LOB.GETLENGTH(Lob_loc);  

    -- first clear the header
    HTP.FLUSH;
    HTP.INIT;

    -- create response header

    HTP.P('Content-length: ' || L_LENGTH);
    HTP.P('Content-Disposition: attachment; filename="emp_data.csv"');
    HTP.P('Set-Cookie: fileDownload=true; path=/');

    OWA_UTIL.HTTP_HEADER_CLOSE;

    WPG_DOCLOAD.DOWNLOAD_FILE( L_BLOB );

  EXCEPTION
    WHEN OTHERS THEN
      DBMS_LOB.FREETEMPORARY(L_BLOB);
      RAISE;
END;