Giving only 3 stars as somehting has changed in version 4.0.6, Mac OS 10.11.6, Firefox 78.4.0esr (64-bit) Right clicking selected text brings up the translation window but the window is blank with spinning ball. I have to click the + sign for the text to go to a new tab at https://translate.google.com. The small popup window doesn't work. I have removed and re-added the extension w/no luck.
The add-on was perfect until just a day or 2 ago. :(