What to check

Check the ribbon cable between the reader and the keypad is connected

Check that the red LED on the reader is on and not flashing.

L1    +12v DC
L2    -12v DC
L3    TX data L2 --- L3 0.5v AC
L4    TX data L2 --- L4 8.7v AC
L5    RX data L2 --- L5 2.0v AC
L6    RX data L2 --- L6 5.8v AC