I2c dark screen

When I upload code to an i2c screen, my lcd screen is dark even when I turn the wheel backwards. What is the reason for this?

my code:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4); // set the LCD address to 0x27 for a 16 chars and 2 line display

void setup()
lcd.init () ; // initialize the lcd

// Print a message to the LCD.
lcd.print("hello everyone");

void loop()

What wheel? The potentiometer on the backpack (the I2C expander board) is for contrast, not backlight. On many of the backpacks there is a jumper to enable or disable the backlight. Is that jumper in place?

I2C back pack CONTRAST

?Is that jumper in place?" what do you mean"

Sorry if I have any basic questions I am new to the field ...

Clearly the jumper is missing, isn't it?
Put a jumper between those two pins.

Oh nice! Sorry for the ignorance .. Thank you very much !!!

Sometimes I wonder if anyone actually sees my posts.

(post deleted by author)

Hmmm. :grin: