WP-Members not using secure ssl link for .css

Hi, it seems that the plug in is not using the https link to include the css in my pages. (It’s the only plugin that isn’t recognizing it)

<link rel=’stylesheet’ id=’wp-members-css’ href=’http://www.xxxxxx.com/xxxxxx/wp-content/plugins/wp-members/css/wp-members-2016-no-float.css?ver=3.1.9.3&#8242; type=’text/css’ media=’all’ />

How do I go about fixing this?

Thanks!