To everyone having problems with the extension.
Please ensure that you went to it's settings and into the last tab "Information" and have no info text asking you to grant it additional permission.

These permissions are needed in order for the extension to work.
It also says so in the V3 changelog:

Added button to enable translation on web pages on the infomation page

>This button is displayed when the extension is not available on a web page due to lack of permissions

Please go to Extensions > 3 Dots for this Extension -> Settings -> Information (In the new Tab) -> Look for a text along the lines of: -> This extension requires more permissions in order to translate on Webpages (Should be below the License and above the Donation)

Did not work

Very good.

Very nice!

The best of firefox "Recommended" translation extensions, has good functional, has in-page selection translations and full-page translations, but not full-page in-page translations. Translate Web Pages extension has that function and all this extension's functions. I don't why this extension IS "Recommended" and TWP isn't
Also:
TWP has multiple translation languages and more translation enginesm right at in-page translation popup. TWP has much more settings. TWP can work with NoScript extension and the current extension can't
So I will remove this extension and use TWP instead, because only advantage of this extension is that it allows you to use more recent languages than TWP (TWP allows maximum 3, which is not enough for me)
P.S. Found a minus: actually can't use DeepL in-page translate because it needs DeepL API which needs not just login, but also your post adress and credit card, which don't work at all in several countries including Russia, it was better if it used copying DeepL Translate data from (background) page or (zero transparency) html iframe

Excellent! I use it everyday.

Es bastante inútil, hay traductores pequeños y muy eficientes, mucho mejores y mas simples de usar

it stopped working for over a week. something wrong with the DeepL API failing. will change review if it ever gets fixed.

doesn't work, changed languages in the settings doesn't change in hover button

Utilisez directement le site Google Traduction pour traduire une page entière, c'est ce que fait cette extension, tout comme DeepL. À la différence que cette extension a accès à tout vos données de navigation. Inutile et très permissif

A melhor extensão de tradução automática que encontrei para o firefox, atendeu as minhas necessidades, achei prática e funcional

Great add-on. It helps me a lot in my everyday hundreds small translations. It will be cool if you add option to copy translated text automatically in clipboard.