Why would this Class D Audio Amplifier have low current draw?
class D if very efficient, it's basically an audio speed buck
  converter. If you are delivering a low voltage to your speakers (maybe
  through not having enough gain), and as they are high impedance
  (16ohm), and with a high supply voltage you might be measuring the
  correct current draw. 2x25 watts would be very loud indeed, are they?
  Are you measuring the current on the correct meter range? Measure that
  of a resistor – Neil_UK 11 hours ago


Neil was right. The voltage delivered to the speakers was apparently pretty low without the gain turned up quite a bit.