Sketch only working while connected to IDE

Using Arduino Programming Questions
1

I'm using a Nano to control a push button, LED, & mp3 player (DFPlayerMini.) When the Nano is receiving normal power, only the push button & LED work.

Why is this only working when hooked up to IDE?

2

Show code, circuit and link to parts used.

4 
#include "mp3tf16p.h"

MP3Player mp3(10,11);


void setup () {
  Serial.begin(9600);
  mp3.initialize();
  pinMode(2, INPUT);
  pinMode(4, OUTPUT);
}

void loop () {
  if (digitalRead(2) == HIGH) {
    mp3.playTrackNumber(1, 30);
    delay(1000);
      }
      else {
        digitalWrite(4, LOW);
      }
}

This is the included library, perhaps the error is somewhere here?

#include "SoftwareSerial.h"
#include "DFRobotDFPlayerMini.h"

#define MP3_ERROR_ONLY 1
#define MP3_ALL_MESSAGE 2

class MP3Player
{
private:
    SoftwareSerial *mySoftwareSerial;
    void statusOnSerial(uint8_t type, int value);
    void waitPlayIsTerminated(void);
    int p_RX;
    int p_TX;

public:
    DFRobotDFPlayerMini player;
    MP3Player(int RX, int TX);
    ~MP3Player();
    void playTrackNumber(int trackNumber, int volume, boolean waitPlayTerminated = true);
    boolean playCompleted(void);
    void initialize(void);
    int serialPrintStatus(int errorOnly);
};

MP3Player::MP3Player(int RX, int TX)
{
    p_TX = TX;
    p_RX = RX;
}

MP3Player::~MP3Player()
{
}

void MP3Player::initialize(void)
{
    mySoftwareSerial = new SoftwareSerial(p_RX, p_TX);

    mySoftwareSerial->begin(9600);
    Serial.println(F("Initializing MP3Player ..."));

    if (!player.begin(*mySoftwareSerial,true,false))
    {
        Serial.println(F("Unable to begin:"));
        Serial.println(F("1.Please recheck the connection!"));
        Serial.println(F("2.Please insert the SD card!"));
        while (true)
            ;
    }
    player.volume(10);
    Serial.println(F("MP3Player online."));
}

void MP3Player::playTrackNumber(int trackNumber, int volume, boolean waitPlayTerminated)
{
    player.volume(volume);
    player.play(trackNumber);
    if (waitPlayTerminated)
    {
        waitPlayIsTerminated();
    }
}

void MP3Player::waitPlayIsTerminated(void)
{
    while (!playCompleted())
    {
    }
}

boolean MP3Player::playCompleted(void)
{
    if (player.available())
    {
        return player.readType() == DFPlayerPlayFinished;
    }
    return false;
}

// Print the detail message from DFPlayer to handle different errors and states.
// 
int MP3Player::serialPrintStatus(int verbose)
{
    if (player.available())
    {
        uint8_t type = player.readType();
        int value = player.read();
        if (verbose == MP3_ERROR_ONLY)
        {
            if (type == DFPlayerError)
            {
                statusOnSerial(type, value);
            }
        }
        else
        {
            statusOnSerial(type, value);
        }
        if(type == DFPlayerError) {
            return value;
        } else {
            return 0;
        }
    }
}

void MP3Player::statusOnSerial(uint8_t type, int value)
{
    switch (type)
    {
    case TimeOut:
        Serial.println(F("Time Out!"));
        break;
    case WrongStack:
        Serial.println(F("Stack Wrong!"));
        break;
    case DFPlayerCardInserted:
        Serial.println(F("Card Inserted!"));
        break;
    case DFPlayerCardRemoved:
        Serial.println(F("Card Removed!"));
        break;
    case DFPlayerCardOnline:
        Serial.println(F("Card Online!"));
        break;
    case DFPlayerPlayFinished:
        Serial.print(F("Number:"));
        Serial.print(value);
        Serial.println(F(" Play Finished!"));
        break;
    case DFPlayerError:
        Serial.print(F("DFPlayerError:"));
        switch (value)
        {
        case Busy:
            Serial.println(F("Card not found"));
            break;
        case Sleeping:
            Serial.println(F("Sleeping"));
            break;
        case SerialWrongStack:
            Serial.println(F("Get Wrong Stack"));
            break;
        case CheckSumNotMatch:
            Serial.println(F("Check Sum Not Match"));
            break;
        case FileIndexOut:
            Serial.println(F("File Index Out of Bound"));
            break;
        case FileMismatch:
            Serial.println(F("Cannot Find File"));
            break;
        case Advertise:
            Serial.println(F("In Advertise"));
            break;
        default:
            break;
        }
        break;
    default:
        break;
    }
}

Picture of Circuit

Additional parts are a 1k, 10k, & 220 Ohm resistors.

5

Hooked up to the IDE, or hooked up to your PC (with IDE closed)? What are you playing the music on? I had a situation where I was playing tracks with Arduino to a Wave Shield, connected to a stereo amplifier/speakers, and it only played when the Arduino was connected via USB to my PC.

The reason was the shared ground between the stereo setup and the Arduino was only through the USB cable to the earthed PC. I had neglected to connect all the grounds together.

6

SOLVED. Thanks for the help, everyone.

There was some type of serial communication issue within the library. I rebuilt the code, simplistically, without any of the extra serial communication.