Thank you for the response! That's great news - that my old AMD Firepro's have been grandfathered in & work with Octane X.

I had previously downloaded the correct version, but I've deleted everything and reinstalled. Now the C4D plug-in is working. It must have been operator error the first time ...

"There is no CUDA device which is supported by Octane Render", when attempting to render within CINEMA 4D R20 with Octane Demo.

I'm using a Mac Pro (2013)
Graphics - AMD FirePro
macOS - Big Sur v11.4

The Octane X download appears be rendering the Target scenes fine.

Do I need a e-GPU w NVIDIA ...