Why can't the i2c scanner see the LCD with the i2c module?

Question

Arduino

Hello! I ordered a 1602A LCD display from China with a module for connecting via i2c. I uploaded the sketch (there were no errors), but nothing comes out. Adjusted the contrast, but nothing. Launched i2c scanner, but writes "No I2C devices found". Why can't he see the display? Plugs connected correctly.
+ when adjusting the contrast, only the top line is lit, the bottom line is visible. Is it a faulty display or what?

PS The module was soldered to the display itself, there is no short circuit.

Answer 1

Did you connect exactly to the correct pins from the arduino side? Is there another device with i2c to check? i2c can be unsoldered and the screen on the wires can be used.

Answer 2

The screen for the operation of this i2c board is not needed at all, it must be determined even if the screen is not connected at all, so it's definitely not the screen.
Check if the wires are connected correctly. You can even ring from the contact on the screen board to the contact on the arduino board, maybe your bundled wires are bad.

Answer 3

If it is connected really correctly, then I would then check the soldering of the i2c module to the screen. In appearance, she directly say "not very". Try cleaning it with alcohol first. If it doesn't work, then solder it.
The squares on the top line are normal.