Hi
Go into device manager and un install the drivers for the 2 display adapters, delete driver files when asked. Restart the laptop when it goes to install the drivers for the display adapters press cancel. You don't want the windows generic drivers to load. The icons will look large and the laptop screen may look out of focus this is normal. Then start Dell driver update from the windows menu this will update / install the drivers and software from Dell for your laptop. If you don't have this program in the Dell start menu group then it is likely the Windows you have is not the image from Dell which will be why the display adapters are not switching.
From the Dell web site :
Dell recommends that you download the device drivers for your Dell PC, printer, tablet, and other Dell devices from the Drivers & Downloads website.
Warning: Downloading and installing device drivers or software from unknown sources may cause the device not to work correctly, cause your PC to crash or not boot into the operating system or sometimes even infect your PC with virus, trojan, or other malicious software.
This from
https://www.dell.com/support/article/nz/en/nzbsd1/sln128938/drivers-and-downloads-faqs?lang=enIf anyone else has an idea here is the specs of the laptop
https://www.dell.com/support/home/nz/en/nzbsd1/product-support/servicetag/0-MjVTUmxjYjg2aEl1T0xGU1RLUTdYUT090/overview#