If you go into any Ground Control Pro preset that is using the expression pedal, you can look at the numbers change on the Ground Control Pro screen as you move the pedal. This should show that the Ground Contro Pro is responding to your expression pedal in real time... and you'll just have to trust me that it also means the Ground Contro Pro is sending the MIDI data at the same time
(actually you can test this too if you have a MIDI interface connected to a computer running a MIDI program like SendSX or MIDI Ox.)
I am quite certain that it has more to do with something in the Kemper that needs attention, although I have no idea where to start there
I found this on the Kemper forum... https://www.kemper-amps.com/forum/index ... tion-time/
It sounds like the same issue, except this poster is even using the Kemper Remote. Unfortunately nothing seems to be resolved there either.