Ignore (Skip) Google RECaptcha validation on Button Click in ASP.Net

I have the following problem, after entering the username and password the code is verified but the code has been verified or not, I can still log in.

Regardless whether the RECaptcha is verified or not when I press the login button, I can start the session but I understand that this should not be possible since it must be verified and the user data provided

Following this example: Google RECaptcha Code with Example in ASP.Net

the code is like this:

<div class="form-group">
	<br /><br /><label for="username">Username</label>
	<asp:TextBox ID="txt_Username" runat="server" CssClass="form-control" placeholder="Username: "></asp:TextBox>
</div>

<div class="form-group">
	<label for="userpassword">Password</label>
	<asp:TextBox ID="txt_pwd" runat="server" CssClass="form-control" placeholder="Password: " TextMode="Password"></asp:TextBox>
</div>

<div class="form-group row m-t-20">
	<div class="col-12 text-right">
		<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
		<script type="text/javascript" src="https://www.google.com/recaptcha/api.js?onload=onloadCallback&render=explicit"
			async defer></script>
		<script type="text/javascript">
			var onloadCallback = function () {
				grecaptcha.render('dvCaptcha', {
					'sitekey': '<%=ReCaptcha_Key %>',
					'callback': function (response) {
						$.ajax({
							type: "POST",
							url: "Login.aspx/VerifyCaptcha",
							data: "{response: '" + response + "'}",
							contentType: "application/json; charset=utf-8",
							dataType: "json",
							success: function (r) {
								var captchaResponse = jQuery.parseJSON(r.d);
								if (captchaResponse.success) {
									$("[id*=txtCaptcha]").val(captchaResponse.success);
									$("[id*=rfvCaptcha]").hide();  
								} else {
									$("[id*=txtCaptcha]").val("");
									$("[id*=rfvCaptcha]").show();
									var error = captchaResponse["error-codes"][0];
									$("[id*=rfvCaptcha]").html("RECaptcha error. " + error);
								}
							}
						});
					}
				});
			};
		</script>
		<div id="dvCaptcha">
		</div>
		<asp:TextBox ID="txtCaptcha" runat="server" Style="display: none" />
		<asp:RequiredFieldValidator ID = "rfvCaptcha" ErrorMessage="Captcha validation is required." ControlToValidate="txtCaptcha"
			runat="server" ForeColor = "Red" Display = "Dynamic" />
		<br />
		<asp:Button ID="btn_Login" runat="server" CssClass="btn btn-primary w-md waves-effect waves-light" Text="Login" OnClick="btn_Login_Click" ToolTip="Ingresar" disabled="disabled"/>
	</div>
</div>

And the code that allows the session to start is the following:

    Protected Sub btn_Login_Click(sender As Object, e As EventArgs)
        If txt_Username.Text.Length <= 1 Or txt_pwd.Text.Length <= 1 Then

            lbl_AlertDanger.Visible = True
            lbl_AlertDanger.Text = "<strong>ERROR</strong> - Wrong credentials"
        Else
            txt_Username.Focus()
            Dim v_Salt As String = "F4!t#+God=$$"
            Dim v_PwdSalt As String = txt_pwd.Text.Trim + v_Salt
            lbl_AlertDanger.Visible = False

            Try
                ds_Student_Login.SelectParameters("Username").DefaultValue = txt_Username.Text.Trim.ToLower
                ds_Student_Login.SelectParameters("Pwd").DefaultValue = getMd5Hash(v_PwdSalt)
                ds_Student_Login.DataBind()

                Dim o_Selecte_UserData As DataView = CType(ds_Student_Login.Select(DataSourceSelectArguments.Empty), DataView)

                For Each o_UserData As DataRow In o_Selecte_UserData.Table.Rows

                    If o_UserData("Result_Cd") = "OK" Then

                        Dim v_CkLastLogin As New HttpCookie("PI_LastLogin")
                        v_CkLastLogin.Values("Username") = txt_Username.Text.ToString.Trim.ToLower
                        v_CkLastLogin.Expires = DateTime.Now.AddDays(30)
                        Response.Cookies.Add(v_CkLastLogin)

                        Session("s_UserID") = o_UserData("User_ID")
                        Session("s_Username") = o_UserData("Username")
                        Session("s_Type") = o_UserData("Type")
                        Session("s_Rol") = o_UserData("Rol")
                        Session("s_UserFullNm") = o_UserData("UserFullNm")
                        Session("s_UserImgProfile") = o_UserData("UserImgProfile")

                        Response.Redirect("Home.aspx", True)
                    End If
                Next
            Catch ex As Exception
                lbl_AlertDanger.Visible = True
                lbl_AlertDanger.Text = "<strong>ERROR</strong> - " + ex.Message
            End Try
        End If
    End Sub