Unable to connect through USB to Tower

I have both versions of the Nexus 7, 2012 and 2013 models. Both are rooted and are running custom5.1 Roms.
Neither tablet will connect via usb to Tower Planner, 3DR services are installed.
Both tablets do connect to Droid Planner2.
Does anyone know why this should be so, does Tower sense a rooted tablet and refuse to work. I know some programs do this.

Thanks in advance.