It is obviously a 5-star extension that should be unnecessary. It is not working in Firefox right now, but it appears to be a Firefox specific issue, since I have another computer that I never update (not Windows or any other software) and it works on that machine, so it must have something to do with Firefox. If I can still see the dislikes even after refreshing YouTube or opening a new tab/window, the dislikes must still be available and we should wait for an update from the dev of this extension.