Presale question about configuration

Hi,
I am running the free version of your plugin on my website kohtourkrabi.com. Before I buy it, I need to make sure that it works fine with my installation. I am running the website on Cloudways (DigitalOcean) and have Varnish enabled. Also, I will be adding Cloudflare to the domain. I am getting mixed responses when trying to use the plugin. Sometimes it works, sometimes it won’t change currency and I am unsure what the best configuration is. On Themeforest I was asked to create a support ticket. Here it is; can you have a look and see if this will cause any issues with the plugin and what the best settings are? I will purchase it once I know it works fine.Thanks!