I am not able to Compute Properties or Optimize to Transition State for a model because these options are greyed out in the MOPAC menu. However, the minimize option in the MOPAC menu is not greyed out, and I can run a MOPAC minimization.
You have a version of Chem3D that does not come with MOPAC Pro, or you have not installed MOPAC Pro yet. Some versions of Chem3D only come with MOPAC Std. You may need to purchase MOPAC Pro separately to use all of the features of CS MOPAC. Some older versions of Chem3D come with MOPAC Pro, but you need to install it separately. Check the ReadMe file on your install disk for information on a MOPAC Pro installer. You might also check the version history page to see if the product you purchased comes with MOPAC Pro. If it doesn't, check our products page for purchasing information.