So, uh, it seems like I'm a cautionary tale. All of my Kemper Player woes are my fault. I go from the Kemper into a looper and thereafter out to monitors. I simply didn't notice that my level out of the Kemper Player was just way, way too damn high. I have some great working profiles.
If you haven't already, be sure to unlink the volume from the master knob once you get your output levels set since you're hitting another device between the player and the amp/monitors. That way you can still use the knob for the other output without hitting the looper too hot.