Primary and both secondary computers are all on Windows 11 with latest updates and all have Multiplicity version 3.6 Build 00105.  Adding both secondary computer brings the new computer to right of grid when connection completes.  Dragging first secondary computer to left of the primary on the grid allows me to move mouse to that computer and control it.  Dragging second secondary computer to the right of the primary puts it there but removes first secondary computer from the grid (goes back to right of the grid).  Both secondary computers allow mouse moves to them when that computer is on the grid but moving the other secondary computer back to the grid always removes the other one back to the side of the grid.  It has always worked fine on these three computers until I upgraded to Multiplicity 4 but then had to roll back to version 3.6 when none of them could connect to primary under version 4.  Note that all three computers showed both Multiplicity 3.44 and Multiplicity 4 under installed apps and trying to uninstall the one labeled 3.44 brings up the version 4 uninstaller.  When I replaced version 4 with a new of version three all three computers now show both 3.44 and 3.6 as installed apps.