If you wire NO switches in series, then all switches must be activated to get a signal through them. Activating a single switch will not be enough. I'm not sure that what you have described can actually work.
So, are you actually using NC switches in series, or NO switches in parallel, or some other configuration? Are there pull-up resistors involved? If so, how are those wired? Are the switch inputs to the Smooth Stepper set up for active-low or active-high operation?