Took a while to figure out why the screen stays black during boot, but I eventually found that the boot menu and apple logo are by default going to an external monitor. I have tried to fix this by resetting the default display in system preferences, SMC and PRAM resets, but to no avail. I'm at a loss as to what is causing this to happen, and can't seem to figure it out. Any help would be appreciated!
Found issue to be in the display assembly. I assume something on the control board got shorted or is not functioning properly, causing EFI to not recognize the screen at boot.