Invisible google captcha v2 is not working properly

Question

The following code is working fine when the form is submitted correctly with all valid data in the first attempt. If there is any server side error after submitting the form then when user resubmits the form the recaptcha does not reset. Following is the sample code:

html-form

<script src="https://www.google.com/recaptcha/api.js"></script>
<div>
<form name="signupForm"  method="POST" action="/signup">
    <div class="form-group mobile-number">
        <input type="tel" id="mobileNo" class="form-control" name="mobileNumber" maxlength="10"
               autofocus>

    <label for="mobile"> Your Mobile no. </label>
    </div>
    <div class="g-recaptcha"
        data-sitekey="{key}"
        data-callback="setResponse"
        data-badge="inline"
        data-size="invisible">
    </div>
    <input type="hidden" id="captcha-response" name="captcha-response"/>
    <button id="submitButon" type="submit">Sign me up!</button>
</form>
</div>

javascript

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

<script>
    function setResponse(response) {
        document.getElementById('captcha-response').value = response;
        submitForm();
    }

    function submitForm() {
        var $form = $("form");
        var data = JSON.stringify($form.serializeObject());
        var myJsonObject = JSON.parse(data);

        data = JSON.stringify(myJsonObject);

        $.ajax({
            type: "POST",
            url: "dummy url",
            contentType: "application/json",
            xhrFields: {withCredentials: true},
            data: data,
            success: function (data, textStatus, request) {
                // success
            },
            error: function (xhr, err) {
                // logics here
                grecaptcha.execute();
                setResponse;
            }
        });
    }
</script>

<script>
    jQuery(document).ready(function () {

        //homepage form
        $('form[name="signupForm"]').validate({
            onfocusout: function (element) {
                $(element).valid();
            },
            rules: {
                mobileNumber: {
                    required: true,
                    minlength: 10,
                    maxlength: 10
                }
            },
// Specify validation error messages
            messages: {
                mobileNumber: "A valid mobile number is of 10-digit",

            },
//submit handler
            submitHandler: function (form) {
                submitForm();
            }
        });
    });
</script>

I think the error is in ajax call but not able to figure out why the captcha is not resetting again.