Karl I just tested and in the reaper i can select KPA driver and it works "but" make sure you have selected 44100 sample rate and deselect following options: (Also try to run reaper as administrator)
Can you explain further please. I am a bit rusty on Reaper.
You said to select a 44100 sample rate but then to deselect the "request sample rate", which in your example is 44100. Where else do you set the sample rate?