Blender 2.9 does not recognize my GPU Until now until Blender 2.83.4 my GPU NVIDIA GeForce GTX TITAN X 12288 MB is recognized via CUDA. With Blender 2.90 and Blender 2.90.1 no GPU is seen, also not under CUDA. What is wrong?
I'am therefor still working with 2.83.4 My computer Mac Pro (mid 2012) 2 x 3,46 GHz 6-Core Intel Xeon / 96 GB 1333 MHz DDR3 - Mac OS High Sierra 10.13.6
Nvidia discontinued the development of the CUDA Toolkit for macOS. The last version that was release for it was 10.2. Consequentially, Blender 2.9x does not include support for CUDA rendering on macOS. This change is documented in the release notes and the manual.

NVIDIA GPU rendering on macOS is no longer supported. Apple dropped support for CUDA drivers in macOS 10.14, and no recent Apple hardware uses NVIDIA graphics cards.


GPU rendering is only supported on Windows and Linux; macOS is currently not supported.

Since Apple has also deprecated their OpenCL compiler it is currently not possible to use GPU rendering with Cycles in Blender 2.9x, until it is ported to Apple's Metal API.
Since Blender 2.83 is an LTS release, I would suggest you continue to use this version.