Whenever comments appear in the Disqus admin but not on the relevant page on your site, this means there are actually two unique discussion threads in Disqus. One thread (with 0 comments) appears on your site, the other thread (with all missing comments) appears in the admin.
Most often this results after changing either your website's URL configuration or the Disqus configuration on your site. For example, this can happen after:
To fix this issue, merge the affected threads using one of our migration tools.