The first thing you'll want to do is verify the steam gauge on the front of the machine. Is there any pressure built up on the right side of the gauge? If not, check the next step for instructions that could solve the issue. If there is pressure built up, skip the next step and move on to the following steps.
The boiler is not on: If the boiler is not on then the hot water tap will not work. The boiler requires steam pressure to be built up in order for the hot water tap to work. If the boiler light is not illuminated or flashing, tap the "B" button so that the "boiler" light starts flashing. In a few minutes you should have steam pressure built up and the boiler light should be illuminated in stead of flashing. If your boiler is already on and fully heated, move on to the next step.
The hot water tap is blocked: Remove the tip of the hot water tap to check the screen for cleanliness. You may have a blockage of debris in the screen not allowing water to pass through.
When you press the hot water button do you hear a "click" audible from the front of the machine?
If you do not hear a click, the solenoid itself may be malfunctioning and need replacing.