Horizontal menu on a web site changed suddenly, no change made to web site

Hello! A web site I frequent, livebyliving.org, has a menu structure running horizontally across the top of the pages. Each option has a pull-down sub-menu. Yesterday afternoon or evening that menu turned into the three bar menu icon in the upper corner of the pages and the horizontal menu disappeared. When I click the three bar icon the entire menu structure is displayed vertically. Firefox on my Android tablet was updated November 26. I used the site in question numerous times since that update and the menu was displayed correctly. It displayed correctly yesterday morning, Nov 29. In the evening, when I went to use the site, the menu behavior had changed. I also note the change when using my Android phone. The last Android update for my tablet was February 6, 2023. I tested with Chrome and Google today and they display the menu correctly so it seems as if something specific to Firefox changed yesterday. I've attached three screen shots. The first is the correct behavior with the horizontal menu. The second image shows the same page with the changed menu presentation. The third image shows the sub-menu presentation after whatever changed. Any thoughts would be most appreciated!