Metrum Acoustic DAC to play Apple Hi-Res using iPhone and iPad

I use a Metrum Acoustic Amethyst DAC. I recently tried playing Hi-Res music from my iPhone and iPad through USB (lighting to USB female then USB male to USB B port of the DAC) with no luck. In the case of iPad I see a HiFace UCA2 device show up but when I play, no audio though the USB even through the USB blue light is on and no error light is seen. In the case of iPhone I do not even see the device to pick and stream to. I suspect it’s the driver required for iOS devices. Any help appreciated