When the LED light is yellow, it means that the Connection Unit is offline, meaning it can't connect to the internet.
First, please verify that the Ethernet cable is properly inserted into the Connection Unit, that the router is switched on and running, and that there are no line/network issues in your area.
If after these checks the LED light remains yellow, please contact your phone operator and request a quick verification of the router, especially the firewalls settings.
If the IRSAP NOW system is already registered and associated through the app, it will work according to the saved settings (e.g. setpoints, time slots).