Thanks Edward for the useful info!
Sorry I didn't make it clear I was not plugging into my audio interface's ST return, but "Main Outs L/R" literally, the ones that's just next to the footswitch and phones ports.
I followed your instructions plugging into ch 7/8, checking on the OL getting things right however my tone still sounds fuzzy and "broken"... Not sure if the problem is my tone so I tried using different tones including the default ones, regardless of clean and distortions its still fuzzy and crappy like my signal is still too hot but my kemper input output is always green light. To provide more info the fuzzy noise is still there even if I lower the track's fader, for gods sake I start to wonder if it's just my speaker's problem
So you can see why I'm confused because at this moment it seems that I could only plug into the Main Outs, however there's no gain control nor I could use the fader to increase the volume, I just couldn't figure out what went wrong
I feel your frustrations buddy i too am going through a very similar scenario (im using SPDIF) sorry this reply aint a solution for you just letting ya know you are not alone ?? hope we both can get a resolve soon.