Wallace,
First are your switches flat?Are you sure? That's usually the biggest culprit.
Next why can't you see under them?
I have a handy little thing I use in my garage on the hot rods(And the trains LOL.). It's a telescoping magnifying mirror . It has a swivel head so you can get it right down there and see whats going on. Not enough light? Just shine your pin light on the mirror , it'll reflect on what your looking at and light it up. You can get one at most auto parts stores.
I do this with mine so I don't have an arc . I disconnect my transformer from the track.
Then I take my voltmeter and set it to Ohms My meter has a tone for continuity I connect the red lead to the middle rail and the black to the outer rail.
Now roll the car thru the switch till you hear the tone .That's where your problem is and you didn't blow a fuse trying to figure it out.
David