Correct operation of the Ajax

Hellow,

Thank you for a good plugin. Maybe I don’t understand, but your form doesn’t work with Ajax in Free (Lite) version?

I’ve tested “Form” with
WordPress v4.9.8
Formidable Forms v3.03
Theme: Twenty Seventeen v1.7
jQuery (//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js)
General settings Formidable Forms checkbox with Ajax – selected

Please tell me where to look for a possible cause?

I’m sorry for my English, It’s not my native language.