Ensure you have the correct USB-to-serial COM port drivers installed so the software can "see" the radio. The Software: RVN4191 was originally sold through Motorola Online

Adjust microphone gain, squelch levels, and configure MDC1200 or DTMF signaling systems.

. Often referred to by its full part number or version (such as RVN4191.14 ), this is the essential Customer Programming Software (CPS) for Motorola’s Commercial Series. RadioReference.com Forums What is RVN4191 Software?