SqlDependency not firing, you're not the only ones. :)
8 years old, i tried using SqlDependency and it failed badly. Today i have another go at it for some weird reasons.
Anyways, if you're having problem with SqlDependency, you're not alone. Try to use this solution instead. The only thing I don't like about it is, change response is given in XML.
Try SqlDependencyEx instead.