Using egpu from Blackmagic with blender. It has the amd radeon pro 580.
Can you go to the log and check the error? You might have to click on the window menu -> Show System console
I run blender from the terminal. I don't know if it is this what you need.
2018-08-23 23:18:03,731 INFO rpr.core_image_cache [123145359495168]: CoreImageCache(original): image_size=None, contexts number=0
2018-08-23 23:18:03,731 INFO rpr.core_downscaled_image_cache [123145359495168]: CoreImageCache(downscaled): image_size=None, contexts number=0
libc++abi.dylib: terminating with uncaught exception of type FrException: TahoeContext: compile failed //// TAHOEERROR: BVH GPU memory allocation failed
Abort trap: 6
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.
[Prozess beendet]
I have two eGPU's of which one is the Blackmagic eGPU and it 'works fine' with the other one which is a Vega 64. I say 'works fine' because at the moment RPR for Blender is a bit temperamental to say the least. Blender sees the BM 580 and during renders it plays a part according to my GPU activity monitor. When you say "It doesn't create anything", do you have a black image in your image editor after the render? I have had that happen a few times the past few days, but if I click the red, green and blue colour channel buttons, I actually see the individual RGB channels... just no combined image.
Can you attach the scene so we can test it?
I just want to say that I think my Blackmagic eGPU is working fine with RPR in Blender. I think the issues I've been bumping into aren't related to the BM eGPU. I'm not getting any error messages when I render using the BM eGPU like @allesdings is experiencing. I'll run a few tests later and report any weird behaviour with specific scenes.