Look at the back of the PSU. On the left you will see a set of thin contacts -- those control the PSU. Do 2 of them have wires/switch soldered to them? The PSU needs those to turn on the DC output...
ref:
Connect the thin brown and black wires together using a small switch and the PSU then supplies power. Green LED will turn on showing that.
Yes, they are soldered by one tiny wire in a "jumper" style, connecting two strips of circuit board together. That's the way it came.