Cannot monitor input signal

I cannot monitor my input signal. It does record and I can hear previous recorded tracks with no problem but cannot hear my input signal while recording a track. I turned on the little green LED for auto input monitoring and that still didn't work. The signal is strong and it records I just cannot hear it in my monitor (headphones).
Pro Tools 12.3.1 MAC OS Yosemite 10.10.5 Duet for ProTools interface

Cannot monitor input signal