Error trying to decode 4K video using NVDEC

I am trying to convert a 4K HEVC MKV file of 70GB into another HECV file but with less size. I am using FFmpeg with Nvidia acceleration but when I execute the following command an error appears:

ffmpeg -y -vsync 0 -hwaccel_device 0 -hwaccel cuvid -c:v hevc_cuvid -i input.mkv -c:a copy -c:v hevc_nvenc -preset slow -b:v 10M -bufsize 10M -maxrate 15M -qmin 0 -g 250 -bf 2 -temporal-aq 1 -rc-lookahead 20 -i_qfactor 0.75 -b_qfactor 1.1 output.mkv

The error is:

[hevc_nvenc @ 0000021036b0d000] Provided device doesn't support required NVENC features
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

The video file has these details:

It seems that FFmpeg cannot recognize my GPU as a supported device to decode but I have read that Nvidia has support for my card with NVDEC.

I am running Windows 10 64 bits with i7 4790 and GTX 1080

NVENC doesn't support encoding B-frames, so -bf 0 and drop -b_qfactor 1.1.