Like so many others, I couldn't get the Sena Device Manager to find my 50s. I have a Mac, running Catalina. I tried to add the Device Manager application to Input Monitoring (via System Preferences>Security & Privacy), as some people have found success doing that. No luck on my end. But then I started wondering if it might the provided USBC to USB cable, which has that wifi/bluetooth monitoring "pack" attached to it.
So I tried a regular USBC > USB cable and bingo! Problem solved.