cant get I2c adapter to work

hello in infancy stages of arduino
i have mega 2560 , i2c adpter lcd display 20x4 character
when load sketch nothing on display
i had display hooked parrallel , printed hello world message
since installing i2c adapter cant print message sketch using
is there missing cause issue


#include <wire.h>
#include <liquidcrystal_i2c.h>

liquidcrystal_i2c lcd(0x20,20,4);

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

  // print message lcd.
  lcd.backlight();
  lcd.print("hello, world!");
}

void loop()
{
}

are absolutely sure i2c adapter on 0x20? have used nick gammon's i2c scanner check?

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