On some Nginx installations the config file does not allow loading the chat widget on the website. Should that be the case you will need to edit the nginx config file.
In your vhost config file you can add in the Server section:
add_header Content-Security-Policy "frame-ancestors 'self' https:;";
Should that not work, you can deactivate the sameorign, however the method above is preferred.
add_header X-Frame-Options "SAMEORIGIN";
#add_header X-Frame-Options "SAMEORIGIN";
Save and reload the site, it should now load the chat widget as expected.