2.7-2.8V Arduino Nano Pro flashing??

Good evening. I have an Arduino nano Pro 3v 8Mhz version and when the voltage gets to 2.79 it looks like it stops running the code and Pin 13 (Onboard LED) starts to flash every second. Is there something in the bootloader that is doing this?

Any help would be appreciated. Thanks!

Sounds damaged to me. Has there ever been an occasion when some pin might have been over voltage. I've done that a few times, and frequently it doesn't bring the whole chip to a halt, but parts of it don't work right anymore.

Do you have a programmer? Check the BrownOutDetection fuse.
If not, you can use an Uno to check them:

I think I have Brown out detection off (BOD) when I go to sleep, Here is the code I am using:

#include <XBee.h>
#include <Vcc.h>
#include <Wire.h>
#include "Adafruit_HDC1000.h"
#include "LowPower.h"


XBee xbee = XBee();
Adafruit_HDC1000 hdc = Adafruit_HDC1000();

uint8_t payload[] = {0,0,0,0,0};

const float VccMin   = 2.1;           // Minimum expected Vcc level, in Volts.
const float VccMax   = 3.1;           // Maximum expected Vcc level, in Volts.
const float VccCorrection = 1.0/1.0;  // Measured Vcc by multimeter divided by reported Vcc

Vcc vcc(VccCorrection);

XBeeAddress64 addr64 = XBeeAddress64(0x0013a200, 0x40c0e33d);
ZBTxRequest zbTx = ZBTxRequest(addr64, payload, sizeof(payload));
ZBTxStatusResponse txStatus = ZBTxStatusResponse();

int switchOneInput = 12;
int batteryLevel = 0;
int switchOne = 0;
int temp = 0;
int hum = 0;
const int sonarPin = 3;
long pulse1;
int inches = 0;

int xBeeWake = 4;


void setup() {
 
  Serial.begin(9600);
  xbee.setSerial(Serial);
  pinMode(switchOneInput, INPUT);
  pinMode(inches, INPUT); 
  hdc.begin(); 
  
}

void loop() {

  sensorRead();  
  
  payload[0] = batteryLevel;
  payload[1] = switchOne;
  payload[2] = temp;
  payload[3] = hum;
  payload[4] = inches;
  digitalWrite(xBeeWake, HIGH);
    delay(3);
   xbee.send(zbTx);
 digitalWrite(xBeeWake, LOW);
  LowPower.powerDown(SLEEP_4S, ADC_OFF, BOD_OFF);
}


void sensorRead(){
    digitalWrite(5, HIGH);
   // Battery level
  batteryLevel = vcc.Read_Perc(VccMin, VccMax);
  if(batteryLevel > 100){
   batteryLevel = 100;}
 
  // Switch Sensor on pin 12
  if(digitalRead(switchOneInput)==HIGH){switchOne = 1;}
  else{switchOne = 0;}
  
  // Temp reading
  temp = (hdc.readTemperature() * 1.8) + 32.0;
  hum = hdc.readHumidity();
  
  // Sonar Sensor
  
  pulse1 = pulseIn(sonarPin, HIGH);
  inches = pulse1/147;
  digitalWrite(5, LOW);
    }

Any idea's on how to disable the BOD permanently through software rather than changing a fuse?

Nope. Need to use a programmer and change the fuse.