Wonderful extension, I use it everyday and I'm very satisfied.

Крутое расширение для мозилы удобно теперь документацию читать программ :В одним словом разработчик красава

Gördüğüm en iyi çeviri uygulaması

Excelente, recomendo, a todos

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)

Very good.