Hi Phil
There is no on / off for the MPG as such.
The MPG axis off indicates that the axis selection switch is in the off position. As you turn axis selection switch it will change to X, Y, Z ,A & B
Until you have an axis selected it will not move.
Also looking at the F1 screen when an MPG is plugged in the minimum you should have showing is one of the 3 resolution inputs should be high depending on which one is selected.
This makes me think you are missing the +ve supply voltage to your pendant because it is the common part of the resolution and axis selection. Pin 1 of the MPG DB 15 socket.
Also the pendant has an led on it to let you know it is powered. Is that lit up on your pendant? I'm assuming yours has one.
You should also be able to measure Masso power supply voltage between pin 1 of the DB15 and the metal surround of the socket which is the -ve.
See the circuit diagram below
https://www.masso.com.au/masso-documentation/?section=mpg-pendant
Hope this helps
Cheers
Peter