Seems I can only get the black Keyes to respond across different zones only a few white Keyes respond to channel aftertouch I haven’t been able to have the sd1 respond to poly aftertouch when using as an midi controller on external midi source.
Usually it’s because the rubber bushings under the keys have hardened up. You can adjust the aftertouch sensitivity in I think one of the System menus. This will help you find out whether the aftertouch is totally dead or if it just takes a lot of pressure.
Sometimes adjusting the aftertouch sensitivity is enough but we also sell a kit of new bushings that make these keybeds feel and respond to aftertouch much better.