I had the same problem, couldn't find any answers on the web. Everyone just says "Goto your Nvidia control panel and change global settings". Duh! That is the first thing I tried and didn't work at all. That answer is no help at all.
The real problem/solution for me was in the monitor, the graphics card drivers were up to date but the laptop had the wrong monitor drivers. It was using the "Basic Microsoft Display" which couldn't change resolution, couldn't brighten/dim the display, and prevented the Nvidia GPU from being used. I went into Device Manager and uninstalled the monitor driver, then clicked the button to search for a new driver online. It ended up installing the "Generic PnP Monitor" driver which I don't think is right but now at least I can change resolution, brighten/dim the display, and use the Nvidia GPU in game.