For some reason I'm not having issues with CloudFlare. If Jon's change of setting is not working for you, there IS a way to add the certificate you extracted into your trusted Root certificates list. IF you have admin privileges on your machine, you can do this.
To get to the right page to add a certificate to your list, you need to get to the control panel. Start by right-clicking the Windows icon at the lower left of your screen. For anything earlier than Windows 10, click Settings and go to Control Panel. For Windows 10, click on the GEAR icon in the popup list. There is "search box" you can use to find settings. Type in "Control Panel" and the ENTER key.
From control panel, select "Network and Internet" >> Internet Options. This brings up a complex dialog box with multiple tabs. It MIGHT be labeled "Internet Properties" but I have Win 10, nothing earlier any more. From there look at the "Content" tab. There is a "Certificates" button that brings up a dialog box that lets you see four categories of publisher. IF you wanted to do so, and IF Jon's adjustment didn't help you, from that Certificates box you could IMPORT the CloudFlare certificate as a Trusted Issuer or as an Intermediate issuer. (There is a button for importing...)
I do not recommend this until you see if Jon's fix helped. I am using HTTPS all the time so my system doesn't balk at the connection but if yours somehow allowed simple HTTP, perhaps Jon's fix will fix you.
NOTE that CloudFlare is NOT in any of my "trusted" or "intermediate" lists either.