Maybe look for other Tinkercad "loose connections". Some of it clearly works because you can run the I2C scanner, however the wiring between the PCF8574 / contrast potentiometer to the display may be faulty. Also ensure you are using a code sample which matches the library you have installed. Maybe you need to explicitly initialise I2C with the Wire library:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);
void setup() {
Serial.begin(115200);
Wire.begin();
lcd.init();
// Print a message to the LCD.
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("Hello, world!");
}
void loop() { }