Hi, I have 8 EI141RC smoke alarms in the house which are interlinked with a wire. Recently I have noticed that they are no longer linked when one goes off (since tested multiple to see if an individual unit issue). I had some work done where a mains cable was cut and then reconnected via a junction box. Is there a way of telling if this is the cause or if the bases/alarms are damaged and need replacing? All were fitted at the same time around 5 years ago so not too old. Many thanks. 

Since the cable was cut and has been repaired I would suggest you start there. You could also check the connections for each alarm are the same.