Ok I check FF. It is getting blocked due to tracking protection. So for Twitter and Instagram, the only way to integrate it well and easily is with embeds/widgets. It is iframed in with some JS code.

So really there isn't a way to fix it and make it work unless you don't use private mode in FF or unblock it.

But if you don't want to do that, I did add a way to disable Twitter and Instagram from the top right menu dropdown. Try it out and let me know if that solves your problem well.