I'am having exactly this problem with my XPS 9570 laptop with Nvidia GTX 1050 Ti. Currently, I am playing Witcher 3. The problem is that the game starts running using the onboard GPU (Intel UHD Graphics 630). The only way I can force the laptop to use NVIDIA GPU, is to use XTU (Intel Software) and run a Stress Test on the CPU. When the CPU reaches 140°F, then the GPU starts working, fps increase to normal ranges. I've been searching on the web for solutions to this, and I have tried everything: updating drivers, uninstall drivers with DDU and install Dells drivers for my GPU and CPU graphic processors, selecting the High Performance GPU on the Panel Control of Nvidia, right click - run with - high processor GPU, etc. I do now see a bit of hope knowing that this is a known problem by the community. Anyone experiencing the same?