shaq writes:

Or you can use DeoxIT, actually improves electrical connections. One
or two squirts will do the trick. They have three spray versions, one
economy one with a flammable solvent, one nonflammable and quick
drying and one with no solvent - just 100% deoxIT.

It sounds like the problem is not with the electrical contacts inside
the switch (because the amplifier does turn on), but with the mechanical
latch mechanism that implements push-on/push-off. And that's probably
due to dried grease.

DeoxIT might actually work to clean the mechanical parts, but that's not
what it's designed for (and it's pretty expensive). I'd clean the
mechanical parts with something like naphtha (lighter fluid), then
relubricate with grease after it had dried.

Dave