Ok, it looks like the PCF8574 has different I2C addresses that are configurable on the LCD. That could be your problem?
In the code that you found worked, what I2C address was being used?
@Gordon started
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Ok, it looks like the PCF8574 has different I2C addresses that are configurable on the LCD. That could be your problem?
In the code that you found worked, what I2C address was being used?