the switch operates a lever in the grating,remove plug and look down drain to check lever is moving when you turn switch,if not then the wire/cable that connects them is broken,ensure wire end is located in switch correctly(a bit like a brake cable on a bike's handlebars)If that seems okay then the screw needs adjusted on the underside of the plug,unscrew as far as it will go without falling apart,ensure lever in drain is up and put plug into hole,turn switch so plug drops and check how much you need to turn screw back so plug closes
steeveepee
November 2008
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix plumbing.