You might need to enable data access permission for it to work.

Go to about:addons, select the addon and go to permission tab and enable permission for the google translate site. For me it is "Access your data *.//translate.google.com" which should be enabled.

Does not work anymore

It is a very good extension. It improve the productivity a lot!

doesnt work anymore

Thanks for this extension. It has improved my productivity a lot!

Shortcuts have stopped working on Nov. 4.
(I believe the cause are changes in Google Translator itself.)