default constructor of "Library::Transaction" cant be referenced -- it's a deleted function

Question

I really don't know what is wrong with my code, I have only pasted the entire code now (EDIT 1).

#include "../../std_lib_facilities.h"

class Date 
{
public:
    Date(int y, int m, int d);
    //...
private:
    int y, m, d;
};

Date::Date(int yy, int mm, int dd)
    :y{ yy }, m{ mm }, d{ dd } {}

enum class Genre
{
    fiction, nonfiction, periodical, biography, children
};

class Invalid {};

class Book 
{
public:
    string book_ISBN() const { return ISBN; }
    string book_title() const { return Title; }
    string book_author() const { return Author; }
    Date book_copyright_date() const { return Copyright_Date; }
    bool availability() { return available; }
    
    Book(string ISBN, string title, string author, Date date, Genre genre);

    void check_out();
    void check_in();

private:
    string ISBN;                         
    string Title;
    string Author;
    Date Copyright_Date;
    Genre genre;
    bool available;
};

void Book::check_out() 
{
    if (available) available = false;
    else throw Invalid{};
}

void Book::check_in()
{
    if (!available) available = true;
    else throw Invalid{};
}

bool operator==(Book a, Book b) 
{
    if (a.book_ISBN() == b.book_ISBN()) 
        return true;
    else 
        return false;
}

bool operator!=(Book a, Book b)
{
    if (a.book_ISBN() != b.book_ISBN())
        return true;
    else
        return false;
}

ostream& operator<<(ostream& os, Book& book) 
{
    return os << '\n'
        << "Title: " << book.book_title() << '\n'
        << "Author: " << book.book_author() << '\n'
        << "ISBN: " << book.book_ISBN() << '\n';
}

Book::Book(string isbn, string title, string author, Date date, Genre genre)
    :ISBN{ isbn }, Title{ title }, Author{ author }, Copyright_Date{ date }, genre{ genre }, available{ true }
{
    int size = 13;
    if (!(isbn.size() == size)) throw Invalid{};

    for (int i = 0; i < size - 1; i++) 
    {
        if (!isdigit(isbn[i])) throw Invalid{};
    }
    if (!(isalpha(isbn[size - 1]) || isdigit(isbn[size - 1]))) throw Invalid{};
}

class Patron 
{
public:
    string patron_username() { return username; }
    int patron_libcardno() { return libcard_number; }
    int patron_libfees();
    bool fee_owed();

private:
    string username;
    int libcard_number;
    int library_fees{ 0 };
};

bool Patron::fee_owed() 
{
    if (library_fees < 0)
        throw Invalid{};

    else if (library_fees == 0) 
        return false;

    else 
        return true;
}

int Patron::patron_libfees() 
{
    if (fee_owed()) 
    {
        return library_fees;
    }
    else 
    {
        cout << "You dont owe any fee";
        return 0;
    }
}

class Library
{
public:
    struct Transaction 
    {
        Book book;
        Patron patron;
        Date date;
    };
    void add_book(Book& b);
    void add_patron(Patron& p);
    void check_out(Book& b, Patron& p);
private:
    vector<Book>Books;
    vector<Patron>Patrons;
    vector<Transaction>transactions;
};

void Library::add_book(Book& b) 
{
    Books.push_back(b);
}

void Library::add_patron(Patron& p) 
{
    Patrons.push_back(p);
}

void Library::check_out(Book& b, Patron& p) 
{
    bool flag1 = true, flag2 = true;
    for (Patron patron : Patrons) 
    {
        if (patron.patron_libcardno() == p.patron_libcardno()) 
        {
            for (Book book : Books) 
            {
                if ((book.book_ISBN() == b.book_ISBN()) && (book.availability() == true)) 
                {
                    b.check_out();
                    flag1 = false;
                    flag2 = false;
                    break;
                }
            }
            if (flag1) 
            {
                throw Invalid{};
            }
        }
    }
    if (flag2) 
    {
        throw Invalid();
    }
    if (p.fee_owed()) 
    {
        throw Invalid{};
    }
    else 
    {
        Transaction transaction;
        transactions.push_back(transaction);
    }
    
}

int main() 
{
    try 
    {
        Book a{ "1234567890123", "boy", "boy", Date{2005, 14, 2}, Genre::fiction };
        Book b { "1234567890123", "girl", "girl", Date{2015, 11, 22}, Genre::nonfiction };
        cout << (a.book_ISBN() != b.book_ISBN());
        cout << a;

    }
    catch (Invalid) 
    {
        cerr << "oopsie daisy" << '\n';
    }
}

Its giving me these two errors:

E1790 the default constructor of "Library::Transaction" cannot be referenced -- it is a deleted function

C2280 'Library::Transacation::Transacation(void)': attempting to reference a deleted function