DaVinci Resolve 17 and GPU error code -999

Hello, I can’t run DaVinci 17 on my ultrabook.
i5 5500U, GT840M 2GB Vram and 12GB DDR3
I have newest drivers, GPU working during playback - increase utylization, but no video, just black screen in preview.

DaVinci need in documentation 4GB of VRAM I have 2GB, but on Windows 10 working flawlessly using 2 GPUs integrated and external.
One for decoding (iGPU) and one for accelerated graphic FX (external).
It is possible to set it up?