“PayPal-Pro gateway requires SSL certificate” Error on site with full SSL

Hi guys,

So I’m getting this error:
PayPal-Pro gateway requires SSL certificate for better security. The force SSL option is disabled on your site. Please ensure your server has a valid SSL certificate so you can enable the SSL option on your checkout page.

My site, https://www.prepmycar.com has a full SSL certificate running across the site. I’ve even tried to add a plugin called: WP Force SSL to see if that works, but not having it. I’ve a site that is almost identical to it and I don’t get this issue. Any ideas on what might be causing it.

For what it’s worth, when it’s active I can still see the form in the checkout as normal and looks fine with no warnings. This is the lander, then just click buy it now to go to the checkout page: https://www.prepmycar.com/car-detailing-101/

Kind regards
Jonathan