Undefined symbols for architecture x86_64 with QNetworkReply

I keep getting the following error: Undefined symbols for architecture x86_64: "checkinapp::myOnFinishedSlot(QNetworkReply*)", referenced from: "checkinapp::qt_static_metacall(QObject*,QMetaObject::Call,int,void**) in moc_checkinapp.o

I have looked through several times and can't figure out where I have gone wrong. (Im new to c++ so im sorry i probably missed something obvious). Any help is appreciated :)

Here is my class:

class checkinapp : public QMainWindow
{
    Q_OBJECT

public:
    checkinapp(QWidget *parent = nullptr);
    ~checkinapp();
    void databasehandler(QWidget *parent = nullptr);
    int stressed;
    int happy;
    int hungry;
    int tired;
    int gender;
    bool help;
    int grade;
    bool submitted;
    void post()
    {
        m_networkManager = new QNetworkAccessManager ( this );
        QVariantMap newUser;
        newUser[ "Stress" ] = QString::number(stressed);
        newUser[ "Sleep" ] = QString::number(tired);
        newUser[ "Hungry" ] = QString::number(hungry);
        newUser[ "Happy" ] = QString::number(happy);
        newUser[ "Grade" ] = QString::number(grade);
        newUser[ "Date" ] = "1/10/21";
        newUser[ "Gender" ] = QString::number(gender);
        newUser[ "Aid" ] = QString::number(help);
        QJsonDocument jsonDoc = QJsonDocument::fromVariant( newUser );
        QNetworkRequest newUserRequest( QUrl( "url/User.jason"));
        newUserRequest.setHeader( QNetworkRequest::ContentTypeHeader, QString( "application/json" ));

        connect(m_networkManager, &QNetworkManager::finished, this, &checkinapp::myOnFinishSlot); // the error is here 

        m_networkManager->post( newUserRequest, jsonDoc.toJson() );
    }
    void exit()
    {
        QApplication::quit();
    }

public slots:
    void myOnFinishSlot(QNetworkReply* x) { exit(); } 
private slots:

    void on_happy_valueChanged(int value);

    void on_hungry_valueChanged(int value);

    void on_sleep_valueChanged(int value);

    void on_stress_valueChanged(int value);

    void on_male_toggled(bool checked);

    void on_female_toggled(bool checked);

    void on_other_toggled(bool checked);

    void on_help_toggled(bool checked);

    void on_pushButton_clicked();

private:
    Ui::checkinapp *ui;
    QNetworkAccessManager * m_networkManager;
    QNetworkReply * m_networkReply;
};

Your declaration

void myOnFinishSlot(QNetworkReply* x)

Does not match your definition:

void myOnFinishSlot()

You effectively defined two methods with different overloads.

Either merge the definition and declaration:

public slots:
void myOnFinishSlot(QNetworkReply* x) { exit(); }

or move the definition outside of the class block:

void checkinapp::myOnFinishSlot(QNetworkReply* x) { exit(); }

Additionally, don't use the SIGNAL/SLOT notation, since it leads to hard-to-debug errors at runtime. Your connect call should be:

connect(m_networkManager, &QNetworkAccessManager::finished, this, &checkinapp::myOnFinishSlot);