The Social Integrations section in Site Performance scans the home page of your website looking for evidence of plugins or links to Facebook, Twitter, Pinterest, Google+ and LinkedIn. If these networks are detected on your website, a green checkmark will appear. If they aren't detected, a red X will appear instead.
There are a few reasons why Site Performance may not be able to detect your social networks:
Your URL and usernames don't match
In order to prevent Social Integrations from detecting unrelated links to social networks on your website, Site Performance compares the usernames on those networks against your website's domain name. If the two don't match, then you may see an X for that social network.
Your links are share links, rather than direct links
Many websites use plugins for sharing pages of a website on a variety of different social networks. Because these plugins aren't specific to your own profile, they are not considered when Site Performance looks for these pages.