How do I get my neighbor to pay for damages to my condo due to his negligence?

I have extensive damage to my bathroom due to a leak in my upstairs neighbor's shower. The leak was found because of a hot water heater break in the unit above his. When the wet walls and insulation from the previous leak were removed, the secondary leak and damages were found. My insurance has denied me coverage saying that the leak has occurred over a period of time so I am not covered. The condo association insurance has claimed the same as well. I opened up a claim through my neighbors insurance but now he refuses to answer phone calls and cooperate with anyone. What do I do!? I am living with wet walls and have confirmed mold from this damage and I also have a 1 year old living in this and no one will pay! I have tried to get my association involved to force the neighbor to become cooperative but they are not helpful either.