I've searched, but I'm unable to find a good photo of the Fn key layout on that model. I wanted to see if you have a Fn key to control screen behaviour. On my old XPS, Fn + F1 controls screen sharing behaviour, selectable from four options: See if you have such a key and use it to select the Extend option.
Hey community, hoping someone can help. I have a new latitude 5430 laptop. I have a screen extender (HDMI to USB c) which worked fine on my previous laptop to extend display to two external monitors. Since I have my new laptop the extender is not working and only mirrors the displays. Everything else is the same except the laptop. Any ideas about why this is happening? I have checked the graphics drivers and they are all up to date. Thanks, Amy 
Latitude 5430 not extending display