Unfortunately old add-on is not compatible with recent Firefox updates anymore. Meanwhile you are still able to install it in old Firefox versions from our website. In case of any problems please contact with details to our support here: https://www.ant.com/support_form
I can't get ANY videos downloaded even after downloading into three (3) browsers - MS Edge, Google Chrome and Firefox. I bought the lifetime version(?) and that hasn't improved my downloading. I suppose that I'll try a competitor as I can't do any worse! :-) Would I recommend Ant Downloader? NOPE!!!! Unless a person has time on their hands or is bored.