Try reconnecting the LCD cable from both the logic board side and the screen side (follow up to 8:25 here https://www.youtube.com/watch?v=ZLNUjeUL4N4&t=324s). If this has happened with no cause, 90% of the time this will resolve your issue. Also, check the backlight cable screen side too, this may be disconnected (right next to LCD cable). Check the screen PCB for any liquid ingress.
Visually inspect the pins on the LCD cable and logic board LCD connector, to check for any melted plastic or burnt pins. Remove the logic board and check it for liquid damage, clean with 95%+ isopropyl if present.
If none of the above works, the logic board will be at fault and will need to be diagnosed. Can point you in the right direction if you have the tools and experience to microsolder, and have the required schematic and board view for your particular logic board. If you do not feel comfortable doing this, your best option would be to send it to a repair shop who have the tools and experience required to do this.