Finally working in Firefox!
Culprit wasn't the apps, because even after disabling all the addons it still wasn't loading.
Once I went into Options -> Privacy -> Untick "Use Tracking Protection in Private Windows"...Facebook Page plugin loads !
That parameter must have been defaulted as ticked by Firefox.
If so then probably alot of users would not have Facebook plugins loaded correctly on the sites they visit if they use Firefox as their browser.
