Hi Chris,
The plugin you are using seems to be blocking everything like scripts, styles, hooks etc. These are essential for other plugins to inject custom HTML.
The only way to get the plugin showing is by including the below HTML and calling the PHP function somehow. You must get help from the plugin dev incase how to get it included.
Paste below HTML in the header or footer of the page
<link rel='stylesheet' id='ufw-style-css' href='https://<YOUR_WEBSITE_URL>/wp-content/plugins/ultimate-floating-widgets-pro/public/css/style.css?ver=5.8.5' media='all' />
<link rel='stylesheet' id='ufw-anim-css' href='https://<YOUR_WEBSITE_URL>/wp-content/plugins/ultimate-floating-widgets-pro/public/css/animate.min.css?ver=5.8.5' media='all' />
<link rel='stylesheet' id='fontawesome-css-css' href='https://use.fontawesome.com/releases/v5.15.1/css/all.css?ver=5.8.5' media='all' />
Call below function in the bottom of the page
UFW_Display::add_widget_box();
Thanks,
Aakash