I have yet to encounter an I2C backpack where the controller wasn't wired in the "standard" way (such that the liquidcrystal_I2C library that doesn't have an option to specify the connections between PCF8574 and LCD works)
However, there are two common I2C addresses used, depending on whether it's a PCF8574 or PCF8574A... Check that. I got screwed on that recently.