I have similar troubles , difficult to understand . Mining dgb groestl with nvidia and ccminer on the blocks factory - works fine. If i use sgminer with amd (rx470 )no way to get any share. On suprnova works well sgminer but no way to make it run with nvidia.
Admins are in holiday ?!
so I spent a few hours trying to figure out sgminer. I'm using a combination of MSI RX 470/480/570 mining with SGMiner 5.1.1 to TBF pool using the following command:
sgminer.exe --gpu-platform 1 -k myriadcoin-groestl -o stratum.dgb-groestl.theblocksfactory.com:9003 -u
It's working great so far. I'm running a 'patched' 16.9.2 driver over 17.5.1 using the method from this post: https://bitcointalksearch.org/topic/m.18857146
Also applied the Pixel Clock Patch https://www.monitortests.com/forum/Thread-AMD-ATI-Pixel-Clock-Patcher
Running Win10
-cryptorex