Not showing output when using pins other than 10 and 11 with SoftwareSerial library on Arduino Mega
From https://www.arduino.cc/en/Reference/softwareSerial:


  Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69).


So you will need to use one of the pins from that list for RX, pin 4 or 5 will not work.