Our house is 2 years old and the hot water in the upstairs bathroom will not work. The sink get's hot water but the tub gets nothing. The tub has a single handle moen fixture. The cold water comes out fine but when you turn the dial to the hot water side, nothing comes out. We at first thought it was a valve that might be turned off but after inspecting everwhere, there was no valve to be found.

If it is the fixture, do I have to turn the main water off? We can't find a cutoff upstairs.