Cannot move participant windows around anymore

Version 6.7.8.  Last Wednesday, all was fine.  Today, less than a week later, I find myself unable to move participant thumbnails around at all anymore.  I’ve always put the speaker directly beneath my laptop camera so I appear to be looking at the speaker, instead of off to the side like I’m paying attention to something else.  A small thing, but I find it offputting so I don’t do it to my meeting participants.   I’ve been using this feature since I started using Zoom during the pandemic, and until today it’s worked fine.  Only options I can see are ‘canned’ sorting arrangements, no provision for turning arrangements off and leaving me to manually arrange participant windows.  How do I get this feature back to working again?