DFPlayer Mini not accepting commands

I am working with a DFPlayer Mini and a Nano.  I am using the FAST library by Powerbroker2 if that matters.    

I want to check the track count using myMP3.numSdTracks()  so I can generate my own random playlist.  The built in one randomAll()  does not seem too random.   It does not always return a useful value though.  Most times I am getting -1 as a response.   Not sure if that is an indication of a comm error or something else.   Any thoughts out there?  Thanks!