The inputs of an LM393 do not work if their voltage is near (within 1.5V) from the positive supply voltage as shown as its Input Common Mode Voltage Range on its datasheet. Your inputs are very close to the positive supply voltage so of course they do not work. But the inputs work perfectly near ground so the current sensing resistor should be in series with the negative terminal of the power bank and ground. An LM393 has a maximum input offset voltage of 5mV which might cause the LED to still be lighted when the charging current is zero so the grounded input should be a few mV positive with two resistors as a voltage divider to correct it.
You have 2k ohms in series with the LED. If the LED is a 1.8V red one then its current will be only 1.6mA which is dim. If the LED is a 3.5V blue one then its current is only 0.75mA and it might be so dim that you cannot see it.
Why short the LED to turn it off? Instead why not have the output of the LM393 going to ground to turn it on? But its output current is fairly low at 10mA.
Do it like this: