How can I fix my Scantronic 9448+ alarm?

I have a Scantronic 9448+ alarm. The lounge movement detector fell off the wall. On refitting, the "tamper" condition prevented me from putting my access code in. What do I have to do? I have tried and got to "engineering mode" but I cannot move on from there. I cannot put in my access code as I cannot reprogramme the settings. Please can anyone help??