Pinterest not loading on older version of Firefox

So I have a bit of a problem. I can't get Pinterest to load normally on older version of Firefox.

It either loads a blank page, or loads partially, without showing the Repin button.

I tried on the latest version of Firefox, Chrome, Brave, and it works fine. But on the older version of Firefox it doesn't.

I tried using a user-agent switcher extension to change the browser and operating system on my older version of Firefox, but still it won't work.

Any ideas how I can.. I don't know.. trick Pinterest into loading properly on the older version of Firefox?

It was an extension that caused the problem, lol...