Gaggia Classic Espresso Machine "syncrony button 26" Questions

Syncrony Compact machine which I am trying to descale. I have added the descaler to the water in the tank. when you hold down the button (26) more than 5 seconds nothing happens.What is the problem To

...Syncrony Compact machine which I am trying to descale. I have added the descaler to the water in the tank but don't know which buttons to press to perform the descale - can you tell me? (Button 26 is ...

...Syncrony Compact Digital. After finishing decaling it showed a message saying Ventilate. I follow the manual i.e. press button 26 and open the knob for hot water then close knob and press button 26 ...