Due to the specification of your computer, you will not be able to switch display.
To display data on the TV screen, connect the cable before you turn on your computer. You can also switch display by restarting your computer.
For your information, the video output of your computer is done at the resolution of 640 x 480 (VGA).
If you select a higher resolution than that, it becomes the virtual display.
You may refer to the Troubleshooting section of the operation manual as well as the online manual for more details.
LCD/external display: The LCD does not display anything.