It seems the addon is removed from Mozilla? I used to use it as it was the best translator addon for many years. I don't like any of the others. The Chrome version is still there but not the Firefox version? Mod the code remove the tracker and host your own personal copy is probably the best option. It isn't that hard to make a small change.

1. S3.Google Translate uses the Google API to ask and provide a translation for the website hence I guess that No Script blocks such requests. How can I disable such block for this specific addon? Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:54.0) Gecko/20100101 Firefox/54.0.
2. S3.Google Translator is a free add-on for the Firefox browser which gives you the power of the Google translator right on your Firefox browser. The app can translate for you automatically an entire webpage, a phrase, or just a text with more than 80 languages available.
3. The addon S3.Google Translator for Firefox by Oleksandr do the translation job for you,just download the add on from Firefox addon site,but note that if you are reading this article with number of tabs opened on your browser,in order for the addon to start its work you need to restart your browser.Like any other addon this addon also resides.

Translator For Firefox

S3.google Translator For Firefox Bookmarks

S3.Translator adds the power of Google Translate’s automatic translations to your browser!
It supports translation of selected text, entered phrase or whole webpage between any of 100+ languages.
New Feature: Language learning!
Installation page:
Mozilla Firefox: https://www.s3blog.org/s3gt.html
Google Chrome: https://chrome.google.com/webstore/detail/s3translator/debnnjfbneojbmioajinefnflopdohjk

S3 Translator Firefox

S3.Translator - this extension for your browser make much easy visit of websites on foreign language.
The extension uses the Google translation public API http://translate.google.com/ and therefore it have more than 100 languages which you can use for quick translation.
Also, the extension able to auto-detect the language of the original text.
There are a lot of simple and complex extensions for browser but they all have same problem: when translating, the format of selected text is lost, while S3.Translator retains the HTML formatting of web pages.
I hope that this extension will be very useful for you.
Canon service tool st4905.