form with recaptcha

hello,

I made my own form for a subscription. I added a recaptcha box to the form;
It works, but when the user doesn’t check the box, they go back to an empty form..
I validate if recaptcha is filled in the post method.
Is there another way to check it? so that the user doesn’t need to start all over again when the box isn’t checked?

De pagina waar ik hulp bij nodig heb: [log in om de link te zien]