If you have removed the bell hold, black wire in your pic and bell did not ring then like others have said either the bell box battery is faulty or like also said probably not connected. Either way you are going to have to get to bell and have a look. Normally two screws either side under a cover to match bell box cover. Remove the cap undo the 2 screws, bell should ring when you remove cover. You should then see probably a green cylinder battery on left, check it is wired to batt pos and neg, if so get details off battery and google for a nèw.

CPX are generally a good reliable domestic alarm.

Ok thank you for that advise i will have a look at the weekend. 

On 18/02/2017 at 10:45 PM, al-yeti said:

If it's a wired bell remove mains and battery both and see what happens 

 

I assume it works if you trigger the alarm when set?

Yes the bell works when i trigger the alarm with key fob as a panic and when it is set. 

So pull the mains and battery then , grab a burger and chill