Quick chat "Loading…" when using HTTPS. HTTP works fine

Quick Chat Version 4.13
Default settings
Wordpress 4.5.2
Create a page
Paste shortcode:
[quick-chat height=”400″ room=”default” userlist=”1″ userlist_position=”left” smilies=”0″ send_button=”1″ loggedin_visible=”1″ guests_visible=”1″ avatars=”0″ counter=”1″]

Open post using HTTP and the chat loads just fine.

When changing the URL to HTTPS only the following happens:

LOADING…
Powered by Quick Chat

https://wordpress.org/plugins/quick-chat/