Trouble Reading Digital Serial on Mega

I am trying to read RS485 serial data that I am converting using a MAX483 to my Mega.

The RS485 serial data is a fixed 5 byte packet and I can see it and decode it easily on my scope on both the RS485 A-B differential side as well as on the MAX483 output pin that is going to the Mega. The levels are about +4vdc. The baud is 9600, and serial is 8N1. My Mega doesn’t see any serial available even though I clearly see the signal on the Mega Digital pin 13 coming from the MAX483. I confirmed the baud rate (9600) with my scope.

I cannot claim this is my own code but adapted from various expert threads from this forum:

#include <SoftwareSerial.h>
#define SERIAL_BAUD 9600 // for PC communications using Serial 0 port
#define SERIAL1_BAUD  9600 // for Arduino

#define SSerialRX        13  //Arduino Receive pin  from MAX483 RO pin 1
#define SSerialTX        12  //Arduino Transmit pin to MAX483 DI pin 4
#define SSerialTxControl 14  //RS485 Direction control on both MAX483 RE and DE. Flips each to reciprocally enable/disable  
#define RS485Transmit    HIGH
#define RS485Receive     LOW

SoftwareSerial RS485Serial(SSerialRX, SSerialTX); // RX, TX

byte buffer[5];
int cnt =0; 

void setup() {
  Serial.begin(SERIAL_BAUD);
  pinMode(SSerialTxControl, OUTPUT);    
  digitalWrite(SSerialTxControl, RS485Receive);  // Init Transceiver   
  RS485Serial.begin(9600);   // set the data rate 
}

void loop() {
  //should find 5 bytes to read 
  while (RS485Serial.available())  //Look for data from other device
  {
    Serial.println("RS485 Data in Buffer");
    if (cnt < 5){
      buffer[cnt++] = RS485Serial.read();    // Read byte into array from cnt = 0-4
    }
    if (cnt == 5){  // all bytes read
      Serial.println("Completed");
      Serial.println(buffer[5]);        // Show on Serial Monitor
      //CLEAR FOR NEXT TIME
      //buffer[] = {0x00,0x00,0x00,0x00,0x00};
    }
    else Serial.println("Problem");

    Serial.flush();
    cnt =0;
  }
  delay(100);
}

Any advice appreciated.