Keyboard Blacklight doesn't work after Ram upgrade

Yesterday I personally upgraded the Ram of my macbook pro, before closing the case I cleaned some dust from the fan and around it. I closed it and everything seemed to be ok, but when it became evening I noticed the backlight won't light up.

After some research I found a Macbook pro teardown, and I was able to see what cable connects the logicboard to the keyboard. It seemed fine, even disconnected the cable and connected it again. Didnt work.

So my question is, should I keep looking at the logicboard or is somehow my keyboard unit broken?

Thanks in advance,

Mike