If power supply is plugged in and not powered on, then +5
volts must appear on purple wire. Purple wire would appear
between gray and yellow wires - second wire in from end of
connector.

Purple wire provides voltage to motherboard logic circuits
so that those logic circuits can tell power supply when to
power on and off. No voltage on purple wire means power
supply is internally defective.

No load is required. Only some supplies require a minimal
load on 3.3, 5, or 12 volts - function unique to each power
supply's design. Some supplies are unstable at near zero
load. Power supply without load will not be damaged. But no
voltage on that purple wire means nothing will work.

Neil Jackson wrote:
I do have a meter, When I stopped working last night. I wasn't
getting any reading whatsoever across anything but the main power
plug.
I dug up the box it came in, and the box indicates that green is
for comm., and the unit itself indicate that this is PS-ON.
Do I have to have a load as well as a switched connection?

Thank you
Neil