Cannot submit with "submit JS script"

[KeithBarrows]

I am trying to submit the form and am having a couple of challenges:

1. The submit button is active even when you do NOT use the captcha - form tries to submit via JS (below)
   2) If you click submit one it fails. If you click submit any number of times after that it just sits and does nothing!

function submitContactUs() {
    if (!$("#frmContactUs").valid()) {
        return;
    }

    $("#btnSubmit").prop("disabled", true);

    let data = {
        ContactType: $("input[name='ContactType']:checked")[0].value,
        FirstName: $("#FirstName").val(),
        LastName: $("#LastName").val(),
        Message: $("#Message").val(),
        AgreeToTerms: $("#AgreeToTerms")[0].checked,
        Email: $("#Email").val(),
        PhoneNumber: $("#PhoneNumber").val(),
        PhoneNumberExt: $("#PhoneNumberExt").val(),
        Product: $("#Product").val(),
        ContactReason: $("#ContactReason").val(),
        Rating: 1 // Set default to pass range validator
    };
    let area = $("#Area").val();

    $.ajax({
        url: 'ContactUs/SubmitContactUs',
        method: 'POST',
        data: data,
        beforeSend: function (request) {
            $("div.ajax_loader").show();
        },
        complete: function () {
            $("div.ajax_loader").hide();
        },
        success: function (data) {
            if (data) {
                if (data === "error") {
                    showMessage(area, "error", "ContactUs");
                }
                else {
                    window.location = data;
                }
            }
            else {
                $("#btnSubmit").prop("disabled", false);
                showMessage(area, "error", "ContactUs");
            }
        },
        error: function () {
            showMessage(area, "error", "ContactUs", null, null, true);
        }
    });
}

What is the best approach to include the postback info required to make the Controller Action work properly. Please note: with this JS code we are not even getting to the Action, we just get a 500 error happening in the Validator with no real message surfaced.

[KeithBarrows]

Removed the nuget, downloaded the repo, added the project to my solution, can trace to a generic error: There was an error validating the google recaptcha response. Please try again, or contact the site owner. This is in the attribute validator.