Heating works but no hot water???

Hm101

There's a panal on my wall. It has a few various buttons for setting the time for heating to come on etc.
Then there are 2 buttons. One says HEATING and the other says HOT WATER.
I've been in the house almost 5 years and normally if you press the hot water button it heats up just the hot water and if you press the heating button it heats up the radiators and the hot water. Now, if I press hot water the boiler doesn't turn on and the water stays cold out of the taps. If I turn the heating on the boiler kicks in and the radiators get hot but there's still no hot water out of the taps or shower.
Does anyone know what this might be and if it's an expensive job to fix???

K.Flyer

It sounds to me that your system has zone valves and the that one that controls the hot water may be faulty or there is something stopping the signal getting to it.
Depending on the make / model whether its the entire valve or the electric controller (actuator) around 200 euro or less. (Could be more id access is difficult)
But have you checked that the thermostat on the cylinder is turned up. The dial will be found on the side of the hot water tank.