how can I make my 3d mouse work again and how do I get my extensions back
@cortiel My experience has been that you always have to re-install 3Dconnection drivers again after an upgrade AND restart computer for it to work again.
Download and install the current version of the 3D Connexion driver software.
Your extensions didn’t go anyway. They would still be installed in the older version of SketchUp. Each version of SketchUp installs separately. For your extensions, download and install fresh up-to-date copies of them from their sources. Don’t copy them unless you want to spend time chasing potential load errors.