Can you open CFX from outside of Workbench? Use the Start Menu -> ANSYS 20XX RX -> CFX. That should open the CFX Launcher. From there click on CFX-Pre and see if there is an error message.
If not you can then open the cfx (or def) file from your Workbench project. If you do not know where these are saved, in Workbench chose View (from the pull-down Menu) and select Files. This will open a window that shows all the files. You want the one in cell B4. You can then right-click and select "Open Containing Folder".
You are navigating away from the AIS Discovery experience