Yesterday I connected my Kemper as always to my DAW via SPDIF and didn't get so much as a squeak.
After some fiddling around I noticed that the issue was limited to my gig profiles that are all setup to use exp1 as a volume pedal.
I use two exp pedals which are not connected when I use the KPA at home/studio.
What I think happened (but I'm not 100% sure since my live equipment is in the rehearsal room) is that I switched off the KPA at the last rehearsal with the volume pedal at the 0 position (the exp1 pedal parameter was at 0 in the MIDI settings). However, turning it up manually in the settings did not fix the issue, still no sound...
My best guess: if you switch of the Kemper, it remembers the last position of the connected expression pedals but something goes wrong when it is switched back on again without those pedals connected.
Did anyone ever experience something similar? I'll connect my pedals again next rehearsal and see if that solves the problem, but in any case, it seems to be a minor bug.