Slimstat plugin and HTTPS not playing nice

I was wondering if anyone uses slimstat with this plugin. When I load slimstat it chrome’s console displays the following error:
The page at ‘https://eatprepd.com/checkout/’ was loaded over HTTPS, but displayed insecure content from ‘http://eatprepd.com/wp-admin/admin-ajax.php’: this content should also be loaded over HTTPS

Any thoughts?

Thanks

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