Dear valued user,
we are sorry for inconvenience you experienced. It seems that you installed depreciated version, which were displayed in the store by accident. The current version works only in Firefox version 49 or higher. To repair the installation please refresh Firefox by the the button "Refresh Firefox" in "about:support" page. Then reinstall "Reverso Context" again. Hope it works, and could you, please, update your review then. Thank you for understanding and support.