I had the same error message but realised my pytorch install didn’t have CUDA installed with it so you can try the conda instructions from above (believe for win10 it’s just conda install pytorch cuda92 -c pytorch)
But I had CUDNN already downloaded so just follow the instructions here (https://docs.nvidia.com/deeplearning/sdk/cudnn-install/index.html). All I needed to do was dump the CUDNN files here C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v10.0\