After I changed 
        ftp to sftp in the script, the error has been resolved! Thank you, @martin!
                
            ftp to sftp in the script, the error has been resolved! Thank you, @martin!
                
            ftp:// to sftp://.
-passive -explicitssl -explicittls  -implicit, as they have no effect with SFTP (and they even contradict one another).
ssh-rsa 4096 hostkey. However, the access is denied. (The hostkey is from Server and Protocol Information Dialog session.)
ssh-rsa 2048 hostkey was operated on other FTP server.