how can I fix my veritas alarm?

My alarm has been working fine up until yesterday .I noticed the unset light flashing.When i pressed the full button on exit it did`nt make the usual noices, and would`nt set.Ive tried pressing the reset button but to no avail.Ive noticed a green light flashing on the main box upstairs.So is it something to do with something inside the box...Hope for your quick response and Thanks for your time