First off always pause the game while trouble shooting. It prevents your other lines from breaking down while trying to find the problem. I had to follow my lines all the way around highlighting each portion until I found the break in the electrical connection. Once I did that the “line” indicators popped up on the tracks and I knew I was back in business.
With TF simple is best. I had a ton of different switches, bridges, crossings etc and I only use a few of them now later in the game.