My front window wash does not work but the back one does?

On my Corsa 2008 model my back window wash is currently working but the front window wash does not. You can hear the pump when you use it but no water is coming through the front window wash and there seems to be no leaks underneath.

I have put warm water and window wash in the water bottle but it still will not work. Please can anyone advise?

Zoe Wareing
December 2010