I have a Fender Champion 100 amp that plays when my guitar is plugged in, but if I try to change the volume, gain, or really any of the knobs the sound is not affected. It’s acting like it’s working properly (certain lights flash when I have certain settings on— those are responding). I also checked the boards and no fuses seem to be blown and no wires are frayed. Nothing seemed to trigger this change. Everything worked fine last time I played.
This amp has 2 separate channels you can switch between with the channel select button in the middle. Only the set of controls for the selected channel will have an effect on the sound. Maybe you inadvertently switched to the left channel so the gain control and everything on the right side is disabled...
I spent some time a few years ago as a Fender warranty repair technician. Occasionally, I would get an amp on my bench that acted as you describe. Almost invariably the amp had taken a blow of some sort and caused the pots to break at the point just above where they were soldered onto the circuit board. This effectively disconnects them from the circuit and renders them useless. You'll probably need to take it in for repair in order to get the proper replacement parts needed to restore the amp to it's proper operation capabilities. I saw more of these problems than most folks might think, but they are easy to fix if you can get your hands on the right parts. Don't despair.