Internal display doesn't work, video out does & internal is detected.

My old MacBook a1278 doesn’t show a picture on the internal display. This is after replacing the thermal paste, which required me to remove the logic board, unplugging each cable connected to it.

I have tried to figure out what I have done wrong in the process of reassembling it, but I am clueless, hence this post.

I have tested various features to make sure they still worked, so I will list them here:

• Webcam works still, green light even turns on.
• Video out via DVI still works, in fact I’m typing this on the laptop in question.

The only thing I have not been able to get working is the internal display, which remains stubbornly blank, thought I will note that it does very briefly turn on, for about a fraction of a second at boot, displaying a slightly brighter shade of black than it does now without end.

Here are my specs, for the MacBook:

• Macbook 5,1
• 2 Ghz Intel Core 2 Duo
• 8 GB Ram
• 1 TB SSD
• Runs MacOS Catalina, 10.15.6, via DosDude’s Patcher

Another note, that I have been running Catalina with no problems for months beforehand, my display issue happened immediately after I reassembled the MacBook after replacing the thermal paste.

Not sure what else is necessary to list here, if I left out some important stuff let me know.

I will also mention that when I close the lid, the laptop goes to sleep, as if no display is plugged in.