Keyboard backlights turns on but turns off when I log it

I recently replaced the screen on my MacBook but what I thought is a camera, I don't know If it is or not. My mac doesn't detect it, so I reopened the MacBook, but when I took everything apart my back light does turn on when I shut down the computer and before I log on but it turns off the moment I log in. How do I fix my backlight when I log into the computer.