I think its just the name and format of the selector you defined...
When using manual selector the use class as start...
For page 1
on button
a.button.input.knewsbutton
or on class of button a#knewsbutton
Or if you wanted to post email submission...
a#btn-widget-prospect.btn-success-widget-prospect (this is from confirmation page modal)
You need to define correctly the element tag selector... I do an inspect of element and use that as a basis.
GLTU