Key points to remember:
1. Domain should only be sample.com without http://.
2. Make sure to paste the html code to your website's index html before the closing body tag </body>.
3. Make sure that the Targeting URLs are properly set.
If you're trying to set targeting to your main website, add a slash at the end.
If you're trying to add a url with subdomain, no need to add a slash at the end.
If you meet these three important points, you're good to go. Else, send us a ticket.
Have a good day!