If your main unit and your phone are no longer communicating, try fully resetting your alarm. In order to do so, follow the steps below:

1) Turn your alarm off and then turn it on again. Wait for around 5 seconds. 

2) Insert the reset code (88008800) using the keypad on the main unit.
3) Press the “Disarm” button for around 5 seconds until it beeps.
 
Then, install the product, following the steps below:
1) Check that your SIM card that is going to be installed in the main unit is properly disarmed (no PIN code) and has credit;
2) Insert the SIM card into the GSM main unit, plug in the power cord and press the ON button;
3) Wait for the GSM signal indicator to start to flash every 3 sec;
4) Download the application, create an account by choosing a name for the alarm, and then inserting the telephone number of the main unit's SIM card.
   

Please note that it is preferable to use the country code if you want to use it from abroad. (E.g. 0044 for the UK. Caution, do not use the symbol + (+44)).
  

Note: It is possible for you to record up to 5 telephone numbers (using the application) allowing the hub to be controlled and warning you.