The error " Lua: error in script" usually means that something that was supposed to be removed was not removeable (during the installation). This can happen during an update (free) or an upgrade (paid).
First, run Permissions Repair with Disk Utility (Mac only), and/or any other system maintenance. This should fix any permissions issues, and allow the uninstall and reinstall to work properly.
If you are a Mac user, drag the Strata Design 3D CX application or application folder from your Applications folder to the trash.
If you are on Windows, Uninstall Design 3D CX.
Then re-install Design 3D CX. This should give you a fresh clean install, and it should open properly.