If you take a look at page 24 of the
old installation guide (pdf) it should give you a rough idea of how the unit is fitted.
If you have a suitable tool to remove one end of the bottom bracket bearing, you should be able to secure the metal ring of the PAS sensor using the bearing cap itself instead of glueing it in place.
I found that it would sometimes work intermittently, and then discovered that the magnet ring needed to be positioned very close to the sensor
(almost touching it) for more consistent operation.
I also found the PAS to be too powerful for my liking, and as my original Pie could not be programmed to reduce the assistance, I ended up removing the PAS from the bike altogether.
If you have the USB programming cable you should be able to fit the sensor on either side of the bottom bracket and then program the controller so it works while pedalling in the forward direction.
If you find it does not respond at all, try turning the magnet ring around on the pedal shaft to see if it helps.
Hope this helps.
Alan