I'm running the default Mozilla Firefox version 68.7.0-lp151.2.42.1.
It's a long time since Google translate did work in Firefox.
Google search works and bring up hitted links, but trying to use "Translate
this page" on any links, only bring up this error message:

Google
400. That���s an error.
Your client has issued a malformed or illegal request. That���s all we know. 

Doing the same procedures using Chromium or Google-Chrome v. 81.0.4044.129-1 
browser do work.

Even copy and paste the translate link from Firefox to Chrome does work with
the latter. 

Sample url follows:
https://translate.google.no/translate?hl=no&sl=en&u=https://fleetworld.co.uk/three-new-citroen-models-with-electric-power-in-2020/&prev=search