Might be a service timer issue:
The Control Panel features three service timers designed to
facilitate the convenient support of service contracts.
Any one, any two, or all three timers can be programmed for
the same or different dates. To disable a service timer simply
program an invalid or expired date. Expired service timers are
automatically cleared when an Engineer code is entered.
Service Timer One - Reminder
Service Timer One is designed to be used as a reminder.
When it expires it turns on high level chime on all eight
zones the first time the panel is set/unset.
Service Timer Two - Nuisance
Service Timer Two is designed to be used as a nuisance.
When it expires it turns on high level chime on all eight
zones every time the panel is set/unset.
Service Timer Three - Lockout
Service Timer Three is designed to be used as a lockout.
When it expires it will turn chime off and the panel will
require an Engineer Reset (see Option 1 page 18 for
details on Engineer Reset).
Anymore info required contact me at info(at) frostsecurity.co.uk
Mike, November 2009