Cannot add new functions to my MPKmini controller via MIDI REMOTE

I can see my Akai MPK mini III,
when i click on the + sign to begin re-mapping my pads, etc (or do i call it, adding cubase functions to my keyboard),
When i click the plus sign, the INPUT AND OUTPUT dialog box shows ‘unavailable’.
Does this mean i cannot assign new functions ? The MPK does show that that pads and buttons have assignments, so Most of this seems to be working.
If I can do this, i imagine it could be done in the STUDIO option, but i can’t see where the problem is.

Please just open the MIDI Remote Mapping Assistant for the Akai MPK mini. You can “overmap” existing factory mappings or create a new custom “user mapping page”.