If you get an error message or the comments don't load, you can use the browser dev tools to see the actual errors and response from server (make sure the debug mode is enabled).
In Google Chrome, right-click and select Element, or use the keyboard shortcut: Ctrl+Shift+I (or Cmd+Opt+I on Mac).
Navigate to the Console tab to see potential JavaScript errors and the Network tab to see the HTTP requests (make sure Record Network Log is on).