Rania switching with

I am a maintenance electrician for well known University in Cambridge UK. We have a installed base of about 300 Rania wireless switches combined with Radio Powr Savr wall and celling sensors.

Quite a bit of the Lutron equipment has been removed because I am told it was "unreliable" but we still have a large installed base which is working fine. I need to maintain that equipment.

I've taken some of the dis-used equipment and tried to set-up a simple test rig for me to learn about the equipment and troubleshoot the devices.

The test rig is very simple
* 1No. Rania switch connected to a 100W incandescent bulb
* 1No. wall sensor paired with the wall switch

I have:
* Replaced the battery in the sensor
* Reset both the wall switch & the sensor (3 button press method)
* Paired the sensor to the switch
* Left the default settings for the sensor i.e. 15mins timeout, low activity, auto-on enabled

The circuit operates perfectly well, manually & in testing:
* the wall switch turns the lamp on & off
* the sensor turns the lamp on & off from it's test buttons
* the sensor lights up in test mode when I walk past it

HOWEVER, I cannot get the sensor to switch the light ON or OFF automatically. No matter how long I leave it, in a small dark room without any occupants.

Three questions:

1. Are all these device likely to be broken, they seem to work fine in testing ?
2. Can you suggest a way to test the equipment other than what I have done ?
3. How can I get the devices to operate as they should be doing ?

Many thanks for any help.

Richard
PS. I've read and tried out every troubleshooting & FAQ publication I can find on the web about these devices !