Ironically, I am having the same problem with a C23, SmoothStepper, Gecko G320's, and Keling Motors. I have followed the setup as best I can figure out, 'cept for SmoothStepper setup where the screens don't look anything like the docs!! I don't know if I have SmoothStepper setup right.
I have SmoothStepper driver and Plugin working, green light on SS lights when Mach starts, SmoothStepper set to power C23, estop string/limit/home setup working, I can reset Mach and led goes out, output lights lit on C23 Step/Dir pins, and C23 main Output light is lit. DRO in Mach moves, but motors don't move. On first hitting cursor up, motor clunks, but doesn't move, then nothing. I have tested AMT encoders with a scope and they work as expected. However, fault light on G320 doesn't come on on power up as it did before I connected motors, but there IS 72 volts at the drive.
I'll try more later, but frustrating for now!! I'll be monitoring this post for replies!!