Review on 🔌 Qunqi IIC/I2C/TWI 1602 Display Module: 16x2 Serial LCD with Blue Backlight for Arduino UNO R3 MEGA2560 by Junior Rojas

High quality screen and accessories. I recommend downloading the i2c scanner sketch to verify the screen address. The one I got was 0x3F. I thought it was DOA and then I realized that there is a contrast adjustment on the serial adapter. Also make sure the pin configuration is correct in your i2c library. The pins are replaced with the chip's serial/parallel port pins, starting at Port0, and not with a physical pin on the chip. You need to open the datasheet of the serial-parallel chip used for validation. This is documented on the web.