This can be caused by images being blocked by Enhanced Tracking Protection. You can check the requests in the Web Console. *"3-bar" menu button or Tools -> Web Developer *https://developer.mozilla.org/en-US/Tools/Web_Console ---- Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content. You can click shield icon for more detail and possibly disable the protection. You can check the Web Console for messages about blocked content. *https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content. *make sure your extensions and filters are updated to the latest version *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems