I would take the view if you have the means to buy a property which is big enough to have power supplies & zone expanders, you should have budgeted for an alarm man.
Reaching for my big book of stereotypes... your from the Clan McSkinflint
As a guess I would assume the Keypad in not communicating with the controls,
Personally I would start by removing a keypad off the wall, connecting it direct to the controls via short bit of wire with nothing else power up or connected to the panels data network & see if you can get control of the panel, then add device one at a time until everything is back on
Just remember the alarm may well have been faulty before the property was void.... good luck