at maximum output voltage on the wiper, 5 V, less about 2 V drop on the LED, leaves 3V/4700 ohm.
you won't see the LED light up - suggest you reduce resistance
however, there is another constraint:
according to the data sheet, maximum current through A, W or B is 2.5 mA
for a wiper at maximum (5V), less 2 V drop on LED, leaves 3V and 2.5 mA - resistor then 1200 ohm
look close to see the LED on.
you might want the wiper to drive a small transistor (2N2222A ? ) and let the transistor drive the LED
can get more V and more current - use 5V and about 330 ohms then LED to collector.
this should make the LED bright and not be a big load on the mcp42...