We are actively engaged with the developers at 3DConnexion and working on the improved integration for Rhino 9 for Mac (RhinoWIP currently). We have a ways to go.
It’s possible in the latest RhinoWIP, it’s possible the newer plugin and the legacy integration are currently interfering with each other. I’m looking into that. In the meantime, please give this a try: RhinoWIP for Mac: Updated 3DConnexion library - #27 by dan
You might have to restart your Mac to get this all working as well.