'Facebook Comments plugin display nothing on Firefox

I integrated Facebook Comments plugin on my web page. I followed Facebook directioons described here https://developers.facebook.com/docs/plugins/comments

For several years everything worked fine, but some two years ago the comments are not visible in Firefox, Opera, Edge, IE. In Chrome everything is fine. This is my testing page: http://kacka.baldsoft.com/test.php

What should I do to display Facebook comments in all browsers?

facebook-comments


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