Can not add rules

I getting white blank popup when I clicking the “Conditional fields Group” button and also when I clicking any other tag generator.
I using this layout

[group advanced-fields]
<fieldset>
<label for="country_code">Country:</label>
[select* country_code data:countries id:country_code include_blank]
<label id="state" for="state_code">State/Province:</label>
[select state_code data:us_subdivisions.states data:us_subdivisions.districts id:state_code include_blank]
</fieldset>
[/group]

I want to show US states if someone choose USA.

How I can do it?