fuzzy tool select not working

[RP380]

   
Hi there.  I use GIMP at work on a PC and at home on a Mac laptop M1 (OSX 13.4.1) .  I have GIMP 2.10.22 (revision 3) on my Mac at home.  I can't get the fuzzy tool to work.  Attached is a screen shot.  I've tried clicking everywhere and changing the settings on the side (first I did a "select none") and no 'marching ants' (I see other references to this lingo- hope it's the right one).

It used to work, but it just stopped working.

With this same image, I can get it work on the PC at work (windows 10).

Does anyone have any fixes?

Thanks kindly

RP