Why does my jar file GUI display perfectly on my computer but not on another computer?

I developed a GUI based application using Java. I used GridBagLayout to build UI. And when I run the jar file on my system the UI is looking perfect as I need. (Please see the below image)

But when I run the same jar file on other machines the UI is like below,

1. Jtextfield became like [] this and not allowing the user to enter the input.
2. Window size changed. You can see the title on the frame is truncated.

Below is the code what I have used in my test pane.

        public TestPane() {
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();

        try {
            URL url = getClass().getResource("alarm5.jpg");
            image = ImageIO.read(url);
        } catch (IOException ex) {
            System.out.println("Error: "+ex);
        }

        Font myFont = new Font("Calibri", Font.PLAIN | Font.BOLD, 16);
        Font myFont2 = new Font("Calibri", Font.PLAIN | Font.BOLD, 14);

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.anchor = GridBagConstraints.WEST;
        selectall = new JCheckBox("Select all");
        selectall.setForeground(Color.WHITE);
        selectall.setOpaque(false);
        selectall.setFont(myFont);
        selectall.addActionListener(this);
        add(selectall, gbc);

        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.anchor = GridBagConstraints.WEST;
        monday = new JCheckBox("Monday");
        monday.setForeground(Color.WHITE);
        monday.setOpaque(false);
        monday.setFont(myFont2);
        monday.addActionListener(this);
        add(monday, gbc);

        gbc.gridx = 0;
        gbc.gridy = 2;
        tuesday = new JCheckBox("Tuesday");
        tuesday.setForeground(Color.WHITE);
        tuesday.setOpaque(false);
        tuesday.addActionListener(this);
        tuesday.setFont(myFont2);
        add(tuesday, gbc);

        gbc.gridx = 0;
        gbc.gridy = 3;
        gbc.anchor = GridBagConstraints.WEST;
        wednesday = new JCheckBox("Wednesday");
        wednesday.setForeground(Color.WHITE);
        wednesday.setOpaque(false);
        wednesday.addActionListener(this);
        wednesday.setFont(myFont2);
        add(wednesday, gbc);

        gbc.gridx = 0;
        gbc.gridy = 4;
        gbc.anchor = GridBagConstraints.WEST;
        thursday = new JCheckBox("Thursday");
        thursday.setForeground(Color.WHITE);
        thursday.setOpaque(false);
        thursday.addActionListener(this);
        thursday.setFont(myFont2);
        add(thursday, gbc);

        gbc.gridx = 0;
        gbc.gridy = 5;
        friday = new JCheckBox("Friday");
        friday.setForeground(Color.WHITE);
        friday.setOpaque(false);
        friday.addActionListener(this);
        friday.setFont(myFont2);
        add(friday, gbc);

        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.anchor = GridBagConstraints.WEST;
        saturday = new JCheckBox("Saturday");
        saturday.setForeground(Color.WHITE);
        saturday.setOpaque(false);
        saturday.addActionListener(this);
        saturday.setFont(myFont2);
        add(saturday, gbc);

        gbc.gridx = 1;
        gbc.gridy = 2;
        gbc.anchor = GridBagConstraints.WEST;
        sunday = new JCheckBox("Sunday");
        sunday.setForeground(Color.WHITE);
        sunday.setOpaque(false);
        sunday.addActionListener(this);
        sunday.setFont(myFont2);
        add(sunday, gbc);

        gbc.gridx = 0;
        gbc.gridy = 7;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridwidth = 2;
        gbc.insets = new Insets(10, 0, 0, 0);
        JLabel env = new JLabel("At what time, should i remind you? ");
        env.setForeground(Color.WHITE);
        env.setFont(myFont);
        add(env, gbc);      

        gbc.gridx = 3;
        gbc.gridy = 7;
        gbc.insets = new Insets(10, 0, 10, 0);
        gbc.fill = GridBagConstraints.HORIZONTAL;
        final JTextField tm = new JTextField(5);
        tm.setText("21:00:00");
        tm.setToolTipText("Input should be in HH:MM:SS format and time format should be 24 hours.");
        add(tm, gbc);

        gbc.gridx = 1;
        gbc.gridy = 8;
        gbc.fill = GridBagConstraints.NONE;
        gbc.gridwidth = 2;
        Set = new JButton(" Set ");
        Set.setFocusable(false);
        add(Set, gbc);
        }

Below is the code what I have used for frame.

                frame2 = new JFrame("Select days and time");
                frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame2.setLayout(new BorderLayout());
                frame2.add(new TestPane());
                frame2.pack();
                frame2.setResizable(false);
                frame2.setLocationRelativeTo(null);
                frame2.setVisible(true);
                frame2.setAlwaysOnTop(true);

Both systems have the same resolution settings. Can you please help me here? how can I make this look same on any system? And how can I fix the JTextfield issue?

Alarm image:

The code you posted is not a minimal, reproducible example. I assume you are setting the image as the background for your TestPane class but the code that does that is missing. The Alarm image you posted is HUGE. I scaled it down to 30% of its original size. After that you just need to call setPreferredSize() in the constructor of class TestPane. For me, a width of 450 and a height of 260 worked well, i.e.

public TestPane() {
    setPreferredSize(new Dimension(450, 260);
    // Rest of your code unchanged.
}

This is how it looks on my computer.