Why not? Am I missing something? Some forum/reddit says that it doesn't even has NVENC. They say just GTX card has those. It is truth for HEVC, but according to these my card (and some others) has NVENC:
If you are still not convinced,
please install Geforce Experience and Nvidia will tell you that shdowplay is NOT supported by your card.
The 840M is from "GeForce" line. But you need a "GeForce GTX" as i mentioned in my 1st post already.