JFrame does not show anything before maximizing

Question

I am trying to do a assignment for school in java. For some reason, when I run the program, it creates the Jframe in the resolution I specified but does not have anything in it. Only after I maximize it does it actually show the components I added.

Also, the maximized frame does show the components but still not in the layout I set. Here is my code:

package Question2;

import javax.swing.*;
import java.awt.*;

public class Fibb extends JFrame {
    public void makeFrame(){
        
        //setting frame attributes
        setSize(1200, 800);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        
        //making objrcts for everything
        GridBagLayout layout = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();
        JLabel numsLabel = new JLabel("1st & 2nd Numbers");
        JLabel seqLen = new JLabel("Length of sequence");
        JTextField firstNums = new JTextField(10);
        JTextField sequenceLength = new JTextField(10);
        JButton generate = new JButton("Generate Sequence");
        JPanel panel = new JPanel();
        
        //setting panel layout to "Grid bag"
        panel.setLayout(layout);
        
        // adding componets in the grid
        gbc.gridx = 0;
        gbc.gridy = 0;
        panel.add(numsLabel);

        gbc.gridx = 1;
        panel.add(seqLen);

        gbc.gridx = 0;
        gbc.gridy = 1;
        panel.add(firstNums);

        gbc.gridx = 1;
        panel.add(sequenceLength);

        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.gridwidth = 2;
        panel.add(generate);
        
        //frame to panel 
        add(panel);
    }

    public static void main(String[] args) {
        Fibb make = new Fibb();
        make.makeFrame();
    }
}

What appears when I run After I maximize

I have tried making the frame start maximized and changing around the resolutions but to no avail. I literally have no idea how to go about troubleshooting.