NVENC not available for encoding

Hello dear Nvidia users.
I am in a pickle and I am not sure where to start.
I just bought an nvidia quadro p400 card for my server, in order to use it for transcoding on emby/plex/jellyfin.
I also want to migrate my video files to h265 8bit so it will be easier to handle by the gpu.

The problem is that NVENC does not seem to be working for encoding and I do not know what to do next.

What i know:
OS. Windows 2016 server, headless, using it through RDP.
Driver version. 431.70, 436.15, 430.86 (I tried these 3) On the official Nvidia website, windows server 2016 is not an option as OS, so I do not know where to get the “latest” ones.

In Emby (premier account) I see options to use NVENC for decoding, but not for encoding.
In Handbrake, I can select h264/h265 NVENC for encoding, BUT when I start the job, the CPU is still being used, the GPU only about 3% and the progress is very slow. On my main pc, I can use Handbrake with same settings, on a GTX1050ti without any issues and progress is very very fast.

How could I check what is wrong, can anybody help me? :)