Hi
Scantronics systems are still amongst the most reliable and Cooper Menvier
who now are Scantronics have a very good archive.
However the 4700 series is no longer with us being superseded by the 500r
and now even that is out of date.
The 4705 pir you refer to IIR has both rear and front tampers and was prone
to a rear tamper fault if the cover was hit causing it to fall off.
Remove the pcb and hold it in your hand pressing both the front and rear
tamper micro-switches then try resetting the panel.
When testing the 4705 PIR detector you must remember that the detector will
go to sleep after an activation for about three minutes to conserve battery
power.

If you have the engineers code you can put the panel in walk test instead.
I have a PDF of the manual should you need it to help in your struggle.
HTH
CJ