Firefox 42+ has a Tracking Protection feature that is enabled by default in Private Browsing mode. Firefox can show a shield icon at the left end of the location/address bar that some content is blocked by Tracking Protection, click the shield icon for more information.

You can disable this feature in "Options/Preferences -> Privacy" or via the about:privatebrowsing page that get when you open a New Private Window.

• Options/Preferences -> Privacy: "Use Tracking Protection in Private Windows"

• https://support.mozilla.org/en-US/kb/tracking-protection-firefox
• https://support.mozilla.org/en-US/kb/control-center-site-privacy-and-security-firefox

You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content.

• https://developer.mozilla.org/en/Tools/Web_Console

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block (wanted) content (e.g. Adblock Plus, NoScript, Ghostery, uBlock Origin) always make sure such extensions do not block (wanted) content.

• make sure your extensions and filters are updated to the latest version

Do you happen to have an ad-blocking extension installed, or remember enabling something called "tracking protection" in Firefox in the past? The page won't load for me with an adblocker running, but if I disable that, it works fine in Firefox.

Thanks you two tracking protection was the culprit changed that and it loads like it should.

You're welcome and thanks for reporting what caused the problem.