If you run older video cards do not update to the latest nvidia 591.xx series drivers. I can confirm for 950M, 1650 Super, and 765M video cards the latest drivers removes hardware encoding. 581.57 seems to be the latest driver version to work and allow nvenc h.264 hardware encoding.
So the sweet spot is after 541 and before 591 for drivers for Nvidia drivers for OBS.
So the sweet spot is after 541 and before 591 for drivers for Nvidia drivers for OBS.