VERY LOW WATER PRESSURE IN THE BOILER

Hello, I am looking for a specialist from gas boilers. In the last days, the water pressure dropped very much - according to the nanometer it is 0.10-0.15 Bara ... and it should ideally be about 1 Bara! I will add that the radiators are still hot. I have full service instructions for this Alpha SY9-24 boiler. I live in Tyrrelstown (D15). Included photo of the front part of the boiler with a pressure gauge. Tel. 0873 915 195.