Accenta 8-system is busy?

I returned from holiday and cancelled the alarm. When later the same day I was going out again, I pressed the first digit of the alarm. That was OK and gave the normal beep. However it would not accept any further numbers. A message came up. System is busy. (By the way for several months there has been a tamper alarm warning but that has not stopped the system working). If I press and hold the RESET switch, I am then invited to type in my code. It accepts this with a beep for each number but then the system is as before with no key plress resulting in a beep. Can you help? I havwe tried the engineers reset code which was suggested to another enquirer (that was 9999, 5, 0 reset, reset) but that made no difference. Thanks

Alan Wood