I've recorded a dry guitar through my UAD Apollo instrument input which I'm now sending to the Kemper which I've set up as an external FX in Cubase.
The signal I'm sending to the Kemper is loud enough. Its just coming back mad quiet. It's more like 60 or 70db from being line level. Even cranking the UA Apollo gain up to the max is not enough.
Amp and Rig volume seem normal to me. It's roughly the same volume output no matter which profile I load.