Hi Mickg65,
Was struggling with the same issue and found a solution:
In Rig Manager options bar PROFILER->Audio Mode, I switched from USB Audio to Native Audio and it allowed me to switch in Cubase to KEMPER PROFILER ASIO driver. Now USB reamping finally works like a charm, had many problems with it on ASIO4ALL.
I had to do the same thing. However, I also found myself being impatient and opening Reaper before the Kemper was 'ready.' By 'ready' I mean that when I selected the Native Audio option, I opened Reaper before the Kemper options for editing showed up at the bottom of Rig Manager.
I initially had Reaper setup for 48000 and to request this setting from the Audio Device, I use a Lynx Aurora. I forgor to untick that option and when I selected the Kemper from the ASIO dropdown, my PC hanged (hung?). I had to hit the power button to shutdown.
Brian