Left turn signal will not work

When I turn on my left blinker, the back left blinker works, but not the front. It doesn't click or have any kind of sound or anything. When I turn it on it does nothing. The right side works perfect. It's not the bulb. I don't know what else this could be? How can I troubleshoot this issue and where should I start? Please give me detailed instructions. Please.

Also to rule this out, I replaced the multi function switch, which is the actual turn signal piece itself, and the relay. The square little box under the steering wheel that plugs right in. I've been trying to fix this project for a while. But years ago I was trying to rule out the problem, and fix some things, so I replaced those two items and it did not fix the issue.