Make sure you have th ebelow libraries.

#include <Wire.h> #include <LiquidCrystal_I2C.h> #include "MAX30100_PulseOximeter.h" LiquidCrystal_I2C lcd(0x27,16,2);

https://www.arduino.cc/en/reference/wire

https://www.arduinolibraries.info/libraries/liquid-crystal-i2-c

https://github.com/oxullo/Arduino-MAX30100/blob/master/src/MAX30100_PulseOximeter.h