Concealed laufen wc doesn't flush - how do I fix it?

My concealed laufen doesn't flush. However, when I remove the air button and blow down it it does. Does that mean that the button isn't pushing enough air (it is pushing air), there is a whole in the bellows (doesn't seem to be), the syphon is stiff or something else. Any help and suggestion of where to get part gratefully welcome.
Many thanks

Rakesh
June 2010