Self Balancing Robot project- wheels only spin in one direction

Yes, I doubled checked to ensure I was set to the correct baud rate but still was receiving these symbols. I believe the issue stems at the arduino/code, as when i detach the power only supplying the arduino, the wheels do not spin at all. I have built many arduino projects in the past but this would be my biggest project so far. My main limitation comes with troubleshooting code. I have posted the mentioned code below:

/*Arduino Self Balancing Robot

#include "I2Cdev.h"
#include <PID_v1.h>
#include "MPU6050_6Axis_MotionApps20.h"

MPU6050 mpu;

// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer

// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorFloat gravity; // [x, y, z] gravity vector
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector

/Tune these 4 values for your BOT/
double setpoint= 176; //set the value when the bot is perpendicular to ground using serial monitor.
//Read the project documentation on circuitdigest.com to learn how to set these values
double Kp = 21; //Set this first
double Kd = 0.8; //Set this secound
double Ki = 140; //Finally set this
/End of values setting***/

double input, output;
PID pid(&input, &output, &setpoint, Kp, Ki, Kd, DIRECT);

volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void dmpDataReady()
{
mpuInterrupt = true;
}

void setup() {
Serial.begin(115200);

// initialize device
Serial.println(F("Initializing I2C devices..."));
mpu.initialize();

 // verify connection
Serial.println(F("Testing device connections..."));
Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

// load and configure the DMP
devStatus = mpu.dmpInitialize();


// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1688); 

  // make sure it worked (returns 0 if so)
if (devStatus == 0)
{
    // turn on the DMP, now that it's ready
    Serial.println(F("Enabling DMP..."));
    mpu.setDMPEnabled(true);

    // enable Arduino interrupt detection
    Serial.println(F("Enabling interrupt detection (Arduino external interrupt 0)..."));
    attachInterrupt(0, dmpDataReady, RISING);
    mpuIntStatus = mpu.getIntStatus();

    // set our DMP Ready flag so the main loop() function knows it's okay to use it
    Serial.println(F("DMP ready! Waiting for first interrupt..."));
    dmpReady = true;

    // get expected DMP packet size for later comparison
    packetSize = mpu.dmpGetFIFOPacketSize();
    
    //setup PID
    pid.SetMode(AUTOMATIC);
    pid.SetSampleTime(10);
    pid.SetOutputLimits(-255, 255);  
}
else
{
    // ERROR!
    // 1 = initial memory load failed
    // 2 = DMP configuration updates failed
    // (if it's going to break, usually the code will be 1)
    Serial.print(F("DMP Initialization failed (code "));
    Serial.print(devStatus);
    Serial.println(F(")"));
}

//Initialise the Motor outpu pins
pinMode (6, OUTPUT);
pinMode (9, OUTPUT);
pinMode (10, OUTPUT);
pinMode (11, OUTPUT);

//By default turn off both the motors
analogWrite(6,LOW);
analogWrite(9,LOW);
analogWrite(10,LOW);
analogWrite(11,LOW);
}

void loop() {

// if programming failed, don't try to do anything
if (!dmpReady) return;

// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize)
{
    //no mpu data - performing PID calculations and output to motors     
    pid.Compute();   
    
    //Print the value of Input and Output on serial monitor to check how it is working.
    Serial.print(input); Serial.print(" =>"); Serial.println(output);
           
    if (input>150 && input<200){//If the Bot is falling 
      
    if (output>0) //Falling towards front 
    Forward(); //Rotate the wheels forward 
    else if (output<0) //Falling towards back
    Reverse(); //Rotate the wheels backward 
    }
    else //If Bot not falling
    Stop(); //Hold the wheels still
    
}

// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();

// get current FIFO count
fifoCount = mpu.getFIFOCount();

// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024)
{
    // reset so we can continue cleanly
    mpu.resetFIFO();
    Serial.println(F("FIFO overflow!"));

// otherwise, check for DMP data ready interrupt (this should happen frequently)
}
else if (mpuIntStatus & 0x02)
{
    // wait for correct available data length, should be a VERY short wait
    while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();

    // read a packet from FIFO
    mpu.getFIFOBytes(fifoBuffer, packetSize);
    
    // track FIFO count here in case there is > 1 packet available
    // (this lets us immediately read more without waiting for an interrupt)
    fifoCount -= packetSize;

    mpu.dmpGetQuaternion(&q, fifoBuffer); //get value for q
    mpu.dmpGetGravity(&gravity, &q); //get value for gravity
    mpu.dmpGetYawPitchRoll(ypr, &q, &gravity); //get value for ypr

    input = ypr[1] * 180/M_PI + 180;

}
}

void Forward() //Code to rotate the wheel forward
{
analogWrite(6,output);
analogWrite(9,0);
analogWrite(10,output);
analogWrite(11,0);
Serial.print("F"); //Debugging information
}

void Reverse() //Code to rotate the wheel Backward
{
analogWrite(6,0);
analogWrite(9,output*-1);
analogWrite(10,0);
analogWrite(11,output*-1);
Serial.print("R");
}

void Stop() //Code to stop both the wheels
{
analogWrite(6,0);
analogWrite(9,0);
analogWrite(10,0);
analogWrite(11,0);
Serial.print("S");
}

This is a course project due on Wednesday, so any help that can readily offered would be appreciated. Thank you.