Apple has a bug in MacOS Catalina that prevents iso image files from burning using any software program including their own. They are aware of the issue but have not indicated if or when they will be fixing it. You can however burn it using Terminal.
- Place the .iso somewhere easy to locate like your desktop
- Insert a blank DVD or BD into your Mac
- Open the Terminal application (Applications > Utilities > Terminal.app)
- Enter the following command:
- Drag your .iso file into the Terminal window (will automatically set the correct path and file)
- Hit Return