I can't use the Gaussian menu. It asks me where the Gaussian application is, so I point it to the CSGaussianClient folder, but I still get an error that the Gaussian application cannot be found.
Gaussian is a separate application that you need to purchase from Gaussian. It is not included with Chem3D. Chem3D comes with a Gaussian *client* - a direct interface to the Gaussian application. You are pointing Chem3D to its Gaussian client, which will not work.