Probably an error. One ohm resistor for R4,5,7. No!
R5,6,7 are not pulled up to 5V.
Please change R4,5,6,7 to 180 ohms. Connect all 4 resistors so then are from 5V to output.
Short out R3. (All LEDs go to ground.)
Now if the output is low (about 0 volts) the LED will be off because the IC will short out the LED.
Now when the output is high it will be about 1.5volts because the current will flow from 5V, through the resistor to the LED. Because the LED turns on and makes light at about 1.5V you will only see 1.5V at the output of the IC. (That is partly why you only see 1.7V now)