Screen isn’t working/Boots to black

I recently opened up my MacBook Pro and replaced the keyboard inside. After closing it up and booting it up, the screen remains dark.

I hooked up an external monitor to it and it did work, I also checked the display setting in the system preferences, and while it did recognize the monitor, the system’s screen wasn’t on the list.

So I figured the problem must be between the logic board and the screen, probably the cable’s connection to the logic board. I made sure the connection was solid, pulled it out and put it back in, made sure the metal lock wasn’t touching the connections behind the socket, but it still didn’t work.

I then proceeded to try and reset the SMC and PRAM, but have no clue if it worked.

I had done this repair with a 17” model and it worked perfectly, so I’m at a loss for what wrong with my system,

Please help!