Scantronic 9800 problem - how can I get it to work?

A Scantronic 9800 was fitted to my house many years ago and the very elderly previous owner lost the codes and did not use it for many years. Not having the access codes meant that the only recourse was to do a reset to the factory settings. I have 'refreshed' the NVM chip as prescribed in the installation manual and checked that the keypad now works with the factory codes etc and also checked that all the settings are as per the factory settings, eg the entry time is set at 1 (10 seconds), the exit time is set at 1 (10 seconds) and the bells and chimes internal and external etc all work. All seemed well so proceeded to normal setting by entering the access code followed by A, sounder on keypad emitted continuous sound with 2 dashes on the screen which clears. When I go out of the exit and lock the door the exit timer stops. When I re-entered there is no sounder emitted from the keypad, the A is illuminated but nothing else. Have tried this a few times and waited for the alarm to start but nothing. Tried leaving the rear door and front door open when setting but nothing comes on the screen to warn that an area is at fault and hence the same result! Am I missing something here? I would be most grateful for any help. Many thanks. Michael