Try adjusting the contrast pot on the back of the display.
Have you set the address correctly?
This may helpful for you: Troubleshooting on LCD I2C
There are several different backpack designs. Some turn on the backlight when powered up and some don’t.
The ones that don’t automatically turn on the backlight require a library to turn it on.
I would recommend installing the hd44780 library (it is available in the IDE library manager)
Take a few minutes to read the included documentation which explains the layout of the library and the i/o classes.
Then run the included diagnostic, I2CexpDiag, which is in the hd44780_I2Cexp i/o class.
If it reports any issues, post the output and we can help you figure out what is wrong.
Once, it reports everything is ok, then you try the other hd4480_I2Cexp i/o class examples.
The benefit of using the hd44780_I2Cexp i/o class is that it will automatically locate the i2c address and self configure for the pin mappings between the i2c i/o expander chip and the LCD.
Terrible photos, taken in darkness from the wrong angle and not focused.
Generally, you need to take the equipment outside in full daylight but not direct sun and use a proper camera in order to take useful photos. Oh well!
You are correct. The backpack has a "pilot" light which should be showing if it has power. Often a nuisance but in this case it is essential!
You need to check your connections. In the second photo it looks as if you have the SDA and SCL directly adjacent to the 5 V connection which would be pins A7 and A6. Do you in fact have the orange wire connected to 5 V? If so, there must be a bad connection in the breadboard or your "Dupont" wires are faulty - you need to test them all or at least switch for other wires until you can get the LED on the backpack to light.