As said above could be diffrent things causing this.
The pump could be stuck , a good tap against it can help.
Broken ....needs replacement
The tube could come lose from the exit of the pump.
All the above needs to be checked by opening the tank from above .
The lid is located under the bottom of the rear wardrobe next to the fridge.
Take the round plastic cap out in the bottom of the wardrobe and you see the lid.
Could be the rubber hose got a knack as WG says but thats a rare one imo. but needs a check.
Could be the tap is broken or stuck inside by "chalk" (translated how we say it in Dutch)
The fact you hear the pump making noise does not mean it's ok. it still can be broken or stuck.
Letting some air in the tank opening the fillercap like
@skinnywhippet says is worth a try , could be vaccuum.
There are treads on how to open the watertank , changing the pump , changing the tap....
Or you could go to the dealer....
