Your inverter needs a minimum amount of solar irradiation in order to be able to start up and function properly. That is also why your inverter is turned off at night When the sun rises in the morning, the inverter will make several attempts to start itself up, the ticking noise you hear is the inverter switching on and off. After a while it will start up and the noise stops. This will occur daily, the length of this procedure can differ depending on daylight conditions. On very cloudy days with low irradiation or when the modules are covered in snow, you may here this sound during the day as well.