help with code for DF player mini

FIXED - I know everything is plugged in correctly because when I use a code that doesnt use the myDFPlayer library from a youtube video it functions properly. However the code i tried to write using the library makes some crackling sounds but doesn't do anything else

NEW PROBLEM - it does play now but only one song unless i hit the next button and its the wrong folder

here's what i've got written
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#include "Arduino.h"
#include "SoftwareSerial.h"
#include "DFRobotDFPlayerMini.h"

SoftwareSerial mySoftwareSerial(10, 11); // RX, TX
DFRobotDFPlayerMini myDFPlayer;

define ACTIVATED LOW

int buttonNext = 2;
int buttonPause = 3;
int buttonPrevious = 4;
int buttonSecret = 5;
boolean isPlaying = false;
boolean start = true;

void setup() {
mySoftwareSerial.begin(9600);
myDFPlayer.begin(mySoftwareSerial);
myDFPlayer.EQ(DFPLAYER_EQ_ROCK);
myDFPlayer.outputDevice(DFPLAYER_DEVICE_SD);
myDFPlayer.volume(15);

pinMode(buttonPause, INPUT);
digitalWrite(buttonPause,HIGH);
pinMode(buttonNext, INPUT);
digitalWrite(buttonNext,HIGH);
pinMode(buttonPrevious, INPUT);
digitalWrite(buttonPrevious,HIGH);
pinMode (buttonSecret, INPUT);
digitalWrite (buttonSecret, HIGH);
isPlaying = false;
}

void loop() {

if (start) {

myDFPlayer.playMp3Folder(02);
start = false;
}

if (digitalRead (buttonPause) == ACTIVATED) {
if (isPlaying){
myDFPlayer.pause();
isPlaying = false;
delay(500);
}
else {
isPlaying = true;
myDFPlayer.start();
delay(500);
}
}

if (digitalRead (buttonNext) == ACTIVATED) {
if (isPlaying) {
myDFPlayer.next();
delay(500);
}
}

if (digitalRead (buttonPrevious) == ACTIVATED) {
if (isPlaying) {
myDFPlayer.previous();
delay(500);
}
}

if (digitalRead (buttonSecret) == ACTIVATED) {
myDFPlayer.playMp3Folder(01);
delay(500);
}

}
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You forgot to add this line to your sketch:

myDFPlayer.begin(mySoftwareSerial);

thanks i changed the post to what the code and problem is now is now.