Excellent app. Sometimes YouTube changes the way the videos are delivered and makes the extension unavailable, but the developers behind the extension works always to bring it alive as fast as they can. This is part of the game, so not their fault. They are amazing, working always to keep the extension updated. If the download button dissapear, just wait for an update. The practice of downloading is not supported by YouTube, so it is nearly a miracle that this team can keep the extension working for so many years. If you don't accept this fact, just don't use the extension, but don't complain.