I went digging through my code, and in my viewDidLoad method, I had the following:
Button1 = NO;
I think I was trying to type out "selected" but got distracted and didn't come back to it, and so was inadvertently turning my own button off. The correct code is:
self.Button1.selected=NO;
[self.Button1 setTitle:@"a" forState:UIControlStateNormal];