1. You need a screen replacement
Your LCD not working properly may be because the screen got damaged because you dropped it or pressure was applied. In this case, we can make the LCD work again simply by replacing the screen.
2. Mainboard damage
A common cause is mainboard damage.
Q: What is the mainboard?
A: The mainboard (motherboard) is the core part of the hardware and controls all functions of the phone. Every part of the phone with a function is connected to this mainboard.
Q: How can the mainboard gets damaged?
A: The mainboard can get damaged from shocks (drops), dropping into water or even from pressure. It can also be caused by charging with a poor quality charger/cable. Damage to the mainboard can arise even if there is no physical damage.
Q: What happens when the mainboard is damaged?
A: As the mainboard is the core part of the device, once it’s damaged, it can make functions play up. The functions affected depend on the location of the damage.