Select the field you want to display based on the value of the OTHER field. Then choose Visibility in the lower right.
You must insert ALL possible values into the top level first. For example, if I want US, Canada, and Australian states to appear when one of those countries is selected, I must put in the entire list to the Field Value box.
THEN, I go into Visibility and do
Choice 1: if Country IS United States, Show State = values
Choice 2: if Country IS Australia, Show State = Values
If you fail to do this, then the form won't work.