What's wrong with my amp

My 3 year old son is always wanting to play my guitar, I have this Line6 30w combo. He used to play with the knobs and would crank it to 10 then switch it on. Now when I turn it on all the lights are on and it still switches between channels but there is no volume, it has a 12" Celestion speaker which is still okay (I've had it checked) If I turn it up full and put my ear close I can just hear it .
Any ideas?
I have to thank him because I was so devastated when I told my wife that she let me get my Marshall MG100DFX. She hates that because I have to turn it up loud to play it, I told her it was because it is a 100w so she let me get my Marshall AVT50, thinking that being only half the power I can play it softer and still be happy with the sound, which I can, 5 on the AVT is not as loud as 5 on the MGDFX.
I'm hoping if I fix the Line6 and put it next to Daddys Marshall he will play his guitar through his amp, I cringe when he grabs the Warlock it is bigger than he is.
Any help will be greatly appreciated, Thanks guys.

The thing about transistors in general is they either work, or they don't.

Somewhere on a circuit board in your Line 6 is one or more unhappy transistors.

I suspect your only option unless its still under warranty, is to take it in to the shop, and prepare to feel some pain. :(