contact form 7 Successful message not showing after submitting

Hi, I am using your Contact form 7.

Facing problem with successful message after submitting. When user submit the form. Successful message shows up for few second and disappear, After that shows empty box with border: check the link please https://imgur.com/Si8W4wd

This is the Code:

<div class=”row”>
<div class=”col-12 col-md-6″>[text* your-name placeholder “Name*”]</div>

<div class=”col-12 col-md-6″>[email* your-email placeholder “Email*”]</div>

<div class=”col-12 col-md-6″>[tel your-phone placeholder “Phone”]</div>
<div class=”col-12 col-md-6″>[text* subject placeholder “Subject*”]</div>
<div class=”col-12″>[textarea your-message placeholder “Message”]</div>
<div>[recaptcha]</div>

<div class=”col-12 align-center”>[submit “Send Message”]</div>
</div>

The page I need help with: [log in to see the link]