I am recording my guitar with my kemper. The kemper is routed to my RME (AN5/6).
In cubase I have monitoring on and I only hear kemper original sound. But I cannot hear any of my plugins in my audio chanel in cubase. Only after I have recorded the guitar and I disable monitoring I can hear the plugins.
Obviously , you monitor the input (source)not the signal post insert.
Create a group (with the fx you want) and feed it with your input channel.
Doing so you can monitor the source earing the fx at the same time.
Cheers !