RStudio Keras CUDA does not work

I am using RStudio
on Windows 10
GTX 1080 (Driver 445.87)
R-Version 6.4
Cuda toolkit 10.2
cudnn 10.2 (copied to the three Folders, lib\x64, bin, include)

I have installed Tensorflow and Keras from GitHub and used:

install_keras(tensorflow = “gpu”)

But when I run Keras, only the processor gets charged.

Where do I make a mistake?

Can anyone help me?

Thank you in advance.