I'm running the latest version of XenForo and the NOVA style on all three of my websites. One of the sites, the WYSIWIG editor buttons are suddenly grayed out and non-functioning in the latest version of Mozilla Firefox. It happens on only one of the forum sites but not the other. I've cleared browser cache - and everything works fine in Microsoft Edge and Google Chrome. I haven't changed any of the settings or options so I'm not sure what could be causing this. Suggestions?