I have the exact same problem, and was just about a start a post asking about this.
I'm trying to control the Keystep using my Kawai ES110's MIDI OUT --> Keystep MIDI IN.
No signal passes through when I press the notes in ES110. This is a huge bummer, i wanted to get a sequence running from Keystep and then play some notes freely on top of it using my external keyboard. Looks like this can't be done using the Keystep. (Of course midi through works as expected as it is simply routing the MIDI data from IN to OUT).
Can someone please confirm if this is indeed a missing/absent feature?. I mean, why would you have a MIDI IN and not support playing in notes from a proper Full Size keyboard?
Being mini-keys it would make sense to accept notes data from external keyboards.
Is this even fixable with a firmware update ? this would be mighty useful, and take the Keystep to another level.
Thanks for answering.