Hi I use various Electro acoustics into my Kemper with zero issues ..can you try yours with another amp or PA ..my thought is that the piezo system on yours may be faulty or there’s a wire loose or suchlike ..
Other thoughts have you got the correct input selected (ie front input ..) stupid but can happen
Try a different cable (again just to rule out ..)
The “aah it’s a Kemper” is just BS