Macbook Pro 2014 doesn't recognize internal display I have a Macbook Pro mid-2014 running macOS Catalina 10.15.3

A few years ago, I dropped it, and broke the screen, then bought a replacement screen and repaired it myself.  Until today, I had no problems with it (except for a minor bug, which I asked about in this question).

Today when I turned my mac on, the internal display does not turn on, but the two external monitors I use work fine.  The internal display is not shown in the display settings, nor in system information -> hardware.

What I've tried:


NVRAM reset
disconnecting the battery from the motherboard, and all cables that are connected to the internal display, then reconnecting
a full reinstall of the OS


I've also tried a plethora of other suggestions, but I don't think they are relevant.

After a bit of research, I suspect the "logic board" might be damaged, but I don't want to spend the money for replacement parts without being certain.


  What can I do to diagnose this problem? Is there anything else I can try?
The fact that your internal display failed, but not your external ones says that the GPU is working.  It suggests that your display is bad, however, it's doesn't rule out the logic board as it could be the video mux chip.

The only way to positively diagnose this issue is to try a known working display on your Mac or connect your display to a known working logic board.  

Since I doubt you have spare MacBook computers laying around, it's best that you take it to a repair shop for diagnosis.