Did you enforce SSL on your site with Really Simple Security, and now some images, stylesheets, or external services are no longer loading?
When a site is requested over the SSL protocol (https), the browser will no longer load resources which are called with the (insecure) http protocol: this is called “mixed content” or “insecure content”. To fix this, Really Simple Security changes all URLs to https://.
However, if you load resources from third-party domains that do not have a valid SSL certificate, these images or scripts will not load: and the result can be a partly broken site.
In some cases, this is caused by an old “staging URL” (e.g., staging.example.com). This URL was used during site development, but the staging URLs are still in place and functioned without issue while the site loaded over insecure http. But on https, this domain will no longer work, and you’ll have to update it to your new domain.
In other cases, the resource might be an online service with a script running from the service’s domain; so the online service should provide the resource over https. In very rare instances, you might encounter services that don’t do this. The recommendation in such cases would be to ask your service provider to enable SSL.
Read this step-by-step article on how to track down mixed content.