Sounds like the warming element has burnt out, after all of these years, or the warming element is not getting current from the power supply inside the Gaggia Syncrony.
Either the electronic panel's power supply is burnt out, or the element finally burnt out with so much use.
There's a coil in there that could have broken, similar to an electric blanket's heating element, or an iron's heating element.
It is unfortunately probably out of warranty from the manufacturer.
So, if you cannot take it apart and look at the power supply and the heating element and test for continuity using a multimeter or a self powered test light, I think that you are out of luck on this one.
I would replace the unit with another if you like Espresso.
I did check their website but found it in Italian and I do not read Italian, unfortunately for me.
http://www.gaggia.it/index.asp