You may have seen some downtime this afternoon. Was doing some maintenance and a little bit of an update.
The update is the Light/Dark mode now functions like it should. In the upper tool bar beside Chat is the toggle. You can set it for Light, Dark, or Auto. Auto will use whatever your Phone or Desktop OS is set to. So, if you have it set to change through the day, the site will as well. If you have it set to be static, so will the site.