I have set up Cloudflare for one of my domains that is hosted on a VDS. When I activate Cloudflare, robots of Facebook, Twitter, GTMetrix cannot fetch required information for them. When I debug this situation with Facebook URL Degubber and Twiter Card Validator, they all give errors such as “Couldn’t resolve host address”.
This is the actual settings I just changed the domain name to example.com and IP address to 123.123.123.123 from element inspection in developer tools before taking the screenshot.
What is your SSL mode set to? Looks like it may be set to Flexible. If you have a certificate on your server (which you should!), switch it to Full and see if this fixes the issue.