How can i reset my scantronic 9800?

The remote reset function does not work, from rt code i type alarm code in then it displays rr then i press clear then 6 but no numbers appear, it just beeps.
How can i reset the panel? It happened when one of the zones in our industrial estate went down, and has not been the same since. It is a fairly old system and the engineer who installed it is no longer available.